Every key we sell is a genuine Microsoft product key, but they don’t all activate — or reactivate — the same way. This page explains each type in plain words: how it activates, what happens when you reinstall, and whether you can move it to a new computer.

Quick comparison

Key type	How it activates	Reinstall on the same PC	New PC or new motherboard
Windows Retail (online)	Enter the key, activates over the internet	Reactivates automatically	Yes — move it, one PC at a time
Windows OEM (online)	Enter the key, activates over the internet	Reactivates automatically	No — stays with the first PC
Phone activation (Windows & Office)	By phone — free Confirmation ID from our Get CID page	Repeat the phone steps (new Confirmation ID)	Retail: yes · OEM: no
Office / Visio / Project online key	Enter the key, activates over the internet	Enter the same key again	Meant for one PC
Microsoft account key (bind)	Redeemed once to your Microsoft account	Download again from your account — no key	Yes — sign in on the new device
Microsoft 365 Premium	Invitation to the subscription	Sign in again	Yes — up to 5 devices at once
Windows Server, SQL Server, RDS CALs	Enter the key on the server	Enter the same key again	One server (CALs stay on your license server)

Windows: Retail vs OEM

Both are full Windows licenses with every feature of their edition. The difference is what happens when you change computers.

Retail belongs to you, not to the PC. When you replace your computer, stop using it on the old one and activate the same key on the new one. It is active on one PC at a time.
OEM is tied to the first PC it activates on — specifically its motherboard. It is the cheapest way to license a PC you plan to keep. If you buy a new computer or replace the motherboard, you need a new key.

Reinstalling on the same PC: once Windows activates, Microsoft remembers that PC (a digital license). Reinstall the same edition, connect to the internet and it activates by itself. If setup asks for a key, choose I don’t have a product key.

Tip for Retail keys: sign in to Windows with your Microsoft account (Settings → Accounts). Your license is then linked to the account, and after a hardware change you can reactivate from Settings → System → Activation → Troubleshoot → I changed hardware on this device recently.

Phone activation keys

Phone activation keys are full Windows and Office licenses for your computer — not for your mobile phone. They are simply activated through Microsoft’s phone activation system instead of the online check, which is why they cost less.

Enter the key. Windows or Office says it cannot activate online (for example error 0xC004C008) — that is expected.
Choose Activate by phone and copy the Installation ID shown on screen.
Paste it on our Get CID page with the activation code from your order. Type the Confirmation ID back in — activated. No call needed.

Reinstalling or changing hardware: the Confirmation ID matches one specific installation. After a reinstall or a major hardware change, Windows or Office shows a new Installation ID and you repeat the three steps. Every phone key includes one Confirmation ID; if you need another one for the same key, message us from your order page and we will issue it.

New computer: Retail phone keys can move — stop using the key on the old PC and activate on the new one with the phone steps. OEM phone keys stay with the first PC.

See the full walkthrough: How to activate Windows or Office by phone.

Office, Visio and Project online keys

An online key activates one installation over the internet. Keep the key safe — it is in your order email and on your order page.

Reinstalling on the same PC: install the same version again and enter the same key.
New PC: the key is meant for one computer. If you replace your PC often, a Microsoft account key is the more flexible choice.

Microsoft account keys (bind keys)

You redeem the key once at setup.office.com while signed in with your Microsoft account. The license then lives in that account permanently.

Reinstalling: sign in at account.microsoft.com → Services & subscriptions and install again. No key needed.
New computer: sign out of Office on the old one and install from your account on the new one. The license covers one device at a time.

Microsoft 365 Premium

A subscription, not a key. You join it with your own Microsoft account, then install the apps from microsoft365.com on as many devices as you like — up to five can be signed in at the same time. Reinstalling or changing devices is just signing in again.

Windows Server, SQL Server and RDS CALs

Windows Server: enter the key in Server Manager or with slmgr /ipk. After reinstalling the same server, enter it again. One license covers one server.
SQL Server: the key unlocks the edition during setup — there is no separate online activation. Reinstalling means running setup again with the same key.
RDS CALs: the pack is installed on your Remote Desktop license server. If you rebuild that server, you reinstall the pack with the same key.

Something didn’t activate?

Every product shows its warranty period on the product page. If a key does not activate within that period, message us from your order page and we send a replacement or a full refund.