What Happens When Your Windows Evaluation Expires
Windows Server installed from evaluation media runs for 180 days. On day 181 it does not stop working and it does not delete anything — it starts shutting itself down every hour. Here is how to find out where you stand, and how to convert it to a licensed copy without reinstalling.
01The Clock You Didn’t Know About
If you installed Windows Server on your own server — with OS Installer or by any other method that pulls Microsoft’s published media — the copy running on that machine came from the Evaluation Center. Those images are free to download precisely because they are time-limited. They install as a fully featured Windows Server with one condition attached: the clock starts at installation and runs for 180 days.
This is not a limitation of the tool that installed it, and it is not something that was hidden from you. It is what the media is. What is easy to miss is that the clock is running from the moment the desktop appeared, and that there is no notification at day 30, 90 or 150 telling you it is there.
During those 180 days the server is not crippled in any way. Every role works, every feature is present, updates install normally, and you can run whatever you like on it. The evaluation is a full product with an expiry date, not a cut-down version.
OS Installer writes the state of your licence and the commands to convert it into the terminal at the end of the run, along with an approximate expiry date calculated from that day. If you installed before that step existed, section 04 below tells you how to find the same information yourself.
02Desktop and Server Are Not the Same
This is the distinction that causes the most confusion, so it is worth getting straight before anything else. Windows 10 and 11 on a server are in a completely different state from Windows Server on a server, and the consequences are not alike.
| Windows 10 / 11 Pro | Windows Server 2022 / 2025 | |
|---|---|---|
| What you installed | The normal consumer media | Evaluation media |
| Time limit | None | 180 days |
| After it lapses | Keeps running indefinitely | Shuts down every hour |
| What you notice | A watermark and blocked personalisation | The machine becomes unusable for anything continuous |
| How to fix it | Enter a product key | Convert the edition first, then activate |
The reason for the difference is that the desktop media is a retail product that ships with a generic volume key already in the answer file, while the Server media is explicitly an evaluation. Those are two different things Microsoft made on purpose, and they behave differently when the licence question is unresolved.
If the desktop you connect to shows a Windows 10 or 11 taskbar, you are in the first row — nothing is going to shut down, and the licence is a question of doing the right thing rather than an urgent one. If you connect to a Windows Server desktop, the clock is real and it is worth finding out where it stands today.
03What Actually Happens on Day 181
When a Windows Server evaluation reaches its end, a service called the Windows License Monitoring Service takes over. It does not lock you out, does not wipe anything, and does not stop the machine from booting. It does something more disruptive in practice: it shuts the operating system down after an hour of running.
Microsoft’s own wording for the event it writes is about as clear as it gets:
“The license period for this installation of Windows has expired. The operating system will shut down every hour.”
In practice it looks like this. The machine runs for an hour. Your remote desktop session drops without warning. You reconnect, and an hour later it happens again. Files are intact and the next boot is normal, so nothing is lost — but anything that needs to keep running cannot. A bot stops. A download stops. A batch job stops halfway. Anything with a session open is interrupted every sixty minutes, forever.
Nobody expects a server to start turning itself off on a schedule. It usually gets diagnosed as a hardware fault, a hoster problem or a crash loop before anyone thinks to check the licence. If a Windows Server you have been running happily for months suddenly restarts roughly every hour, check the licence before you open a ticket with your provider.
For an unactivated Windows 10 or 11 the experience is much milder and much more familiar. A watermark sits in the bottom corner reading Activate Windows. Personalisation settings are refused, so you cannot change the wallpaper or the theme colours. Windows reminds you periodically. Performance is not affected, security updates still arrive, and the machine does not shut down. It will keep working like that for as long as you leave it.
04Check Where You Stand
Two commands on the server tell you everything. Open PowerShell as administrator.
DISM /online /Get-CurrentEdition
The word you are looking for is Eval. An answer of
ServerStandardEval means you are on an evaluation. If it returns
ServerStandard without the suffix, the machine is on a real licence and none
of the rest of this applies to it.
slmgr /dlvThis prints a block of licence detail. Two lines matter: the evaluation end date, and the remaining rearm count. Write the date down somewhere you will see it again — the whole problem with a 180-day clock is that it is long enough to forget.
On Windows 10 or 11 you can skip the commands and open
Settings, System, Activation, which states plainly whether the machine is
activated. slmgr /dlv works there too if you prefer the detail.
The conversion in the next section needs the machine to be up and reachable, and it needs a reboot. Neither is a problem today. Both become considerably more irritating when the machine is shutting itself down every hour while you try to type commands into it.
05Converting a Server Evaluation to a Real Licence
Here is the part that catches almost everybody. You cannot activate a Windows Server evaluation by opening Settings and typing a product key. That box exists and it will not do the job. An evaluation has to be converted to a retail edition first, and the tool for that is DISM.
The good news is that conversion keeps everything. Your files, your applications, your roles, your configuration — all of it stays. It is an edition change on a running installation, not an upgrade and not a reinstall.
DISM /online /Get-CurrentEdition
DISM /online /Get-TargetEditionsThe second command tells you exactly which editions you are allowed to move to. Use the name it prints rather than assuming, because the rules are stricter than most people expect.
DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula
Replace the placeholder with the key you own, and replace ServerStandard with
whichever target edition the previous command listed. When it finishes, reboot.
slmgr /atoWhat converts to what
| You have | You can convert to | Notes |
|---|---|---|
| Eval Standard, Desktop Experience | Standard or Datacenter | Widest set of options — this is the usual case |
| Eval Datacenter | Datacenter only | Cannot come down to Standard |
| Eval Standard, Server Core | Datacenter Core only | Cannot become Standard Core after the fact |
| Evaluation running as a domain controller | Nothing | Must be demoted first, if that is even an option for you |
An evaluation of Standard in the Server Core installation option cannot be converted to a licensed Standard Core — it can only go to Datacenter Core. Nothing OS Installer deploys is Core; it installs the Desktop Experience edition, which is the row with the most freedom. But if you built a Server Core VM yourself from evaluation media, check the table before you buy a key.
What about rearming?
There is a documented procedure for extending an evaluation, called rearming, and a fresh installation allows it up to six times. Six periods of 180 days is three years of evaluation. Microsoft publishes it because evaluating a product for longer is a legitimate thing to want.
It is also not a licensing strategy. Rearming extends a trial; it does not make the installation licensed, and treating three years of extensions as a substitute for buying the product is a misuse of something Microsoft provides in good faith. If the machine has settled into real work, the honest answer is a licence.
06Licensing Desktop Windows
Windows 10 and 11 Pro are simpler, because there is no evaluation edition to convert. The edition already installed is the one you want — what it lacks is a real key.
slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
slmgr /atoOr use the interface: Settings, System, Activation, Change product key. No reboot is strictly required, though one does no harm.
One thing worth understanding about what the installer put there. The key in a fresh installation like this is a generic volume licence key — a key Microsoft publishes openly for every edition. On its own terms, Microsoft states that these keys
“won’t activate or serve as a retail license key.”
What it does is put Windows into KMS client mode, so a machine on a corporate network finds an activation server automatically. On a server with no such host, nothing happens: the edition is correct and the activation is simply unresolved. That is the exact state your install is in, and it is why entering a real key is all that is needed.
A retail licence can be moved to a different machine later. An OEM licence is tied to the first machine it is installed on and is generally not transferable. On a server you might replace or rebuild, retail is the version that does not need buying twice — which is worth more than the difference in price.
07The Grey Market Trap
Once you know you need a key, it takes about thirty seconds to find somebody selling one for a fraction of the retail price. It is worth understanding exactly what you are buying at that price, because the failure mode is delayed and unpleasant.
The cheap keys on resale sites are frequently volume or corporate keys rather than retail ones. They activate, because they are real keys for the right product. Then at some point Microsoft deactivates the key — because it was never legitimately sold to you in the first place — and your Windows reverts to unactivated, sometimes months later, often with no explanation. There is nobody to complain to. You have no support entitlement because you are not the licensed customer.
A legitimate Windows licence costs many times more than the tool that installed it. That looks odd at first and is completely normal: you paid a small amount for a deployment, and you are being asked a larger amount for an operating system. They are different purchases. If the licence price feels disproportionate, compare it against what the machine is doing, not against what it cost to set up.
The safe route is unglamorous: buy from the vendor’s own store, or from a reseller who is an authorised Microsoft partner and will show you the paperwork. If a price looks too good to be true and the seller will not state plainly what type of licence they are selling you, that is the answer.
This article describes documented behaviour and the commands Microsoft publishes for it. Licensing rules change, differ between situations and depend on details only you know. For anything that matters commercially, confirm it with Microsoft or an authorised reseller.
08Frequently Asked Questions
Will my Windows Server really shut down every hour?
Yes, if it is an evaluation that has reached its end. The Windows License Monitoring Service shuts the operating system down after roughly an hour of running, and it repeats. Nothing is deleted and the machine boots normally afterwards, which is exactly why it gets misdiagnosed as a hardware or hosting fault. The licence is the first thing to check when a Windows server starts restarting on a regular rhythm.
Can I just keep rearming instead of buying a licence?
You can rearm six times, which is three years, and Microsoft documents the procedure openly. It is intended for people who are still evaluating. Using it to run a machine that has become permanent is a misuse of a mechanism provided in good faith, and it leaves you on an unlicensed installation with a clock on it. For anything real, the licence is the answer.
Does converting the edition delete my files or applications?
No. Conversion changes the edition of the installed operating system in place, keeping your data, your applications, your roles and your settings. It takes a while and it needs a reboot, so do it at a moment when a reboot is convenient — but it is not a reinstall and it is not destructive.
Can I move from an evaluation to Datacenter instead of Standard?
From an evaluation of Standard with the Desktop Experience, yes — that row has the most options and Datacenter is one of them. What is not possible is going the other way: an evaluation of Datacenter can only ever convert to Datacenter, never down to Standard. Run DISM /online /Get-TargetEditions and let it tell you rather than assuming.
Do I need to reinstall Windows to license it?
No, and this is the most common misconception about evaluations. Everything already installed becomes licensed by the conversion. You do not lose the machine, you do not rebuild it, and you do not need to install Windows again. That is true for Server, where DISM handles the conversion, and for desktop Windows, where entering a key is all that is required.
I have Windows 10 running unactivated. Is that urgent?
Not in the same way. An unactivated desktop Windows keeps running indefinitely with a watermark, blocked personalisation and periodic reminders — there is no hourly shutdown, because that behaviour belongs to evaluation editions rather than unactivated retail ones. It is not urgent, but it is also not a licensed machine, and entering a key you own fixes it in about a minute.
Windows on your server, licence understood
OS Installer deploys Windows 10 Pro, Windows 11 Pro, Windows Server 2022 or Server 2025 on your Ubuntu 24.04 server over SSH, and tells you at the end exactly which licence state you are in and how to change it.