Installing and activating Office for Windows

This guide covers Office 2021, 2019 and 2016 Professional Plus, Project 2021 and Visio 2021 on a Windows PC. Along with your key, you receive by email a link to Microsoft's official installation file. The whole process takes about 20 minutes, and for most of that time Office installs itself. There is a separate guide for Mac.

Before you start

  • An internet connection — activation goes through Microsoft's servers.
  • Windows 10 or Windows 11 and about 4 GB of free space.
  • No other version of Office on the computer, including the Microsoft 365 trial that comes with most new laptops. Two versions on one PC are the most common reason a key is not accepted.

Step 1 — remove the old version

Open Settings → Apps → Installed apps. Find Microsoft 365 or Microsoft Office, click the three dots on the right and choose Uninstall. Then restart the computer.

Settings, Installed apps: the three-dot menu next to Microsoft 365 and the Uninstall command
The old version is removed from Settings → Apps → Installed apps.

If uninstalling stops halfway, see how to remove an old version of Office completely.

Step 2 — download the installation file

Open the link in the email with your key. A file with the .img extension downloads — for example ProPlus2021Retail.img for Office 2021. It is about 4 GB and comes straight from Microsoft's server.

Don't download Office from other websites. The installation file is free — you only pay for the licence.

Step 3 — open the file and start the installation

  1. Double-click the downloaded .img file. If it doesn't open, right-click it and choose Mount. Windows shows it as a DVD drive — no extra software needed.
    Downloads folder: the ProPlus2021Retail.img file and the Mount command in the right-click menu
    Open the .img file with a double-click or right-click → Mount.
  2. In the new drive, double-click Setup. When Windows asks whether to allow changes to your device, choose Yes.
    DVD drive with the Office files: Setup is highlighted
    The installation starts from the Setup file.
  3. The installation runs on its own for 5–15 minutes. At the end a message says Office is installed — click Close.
    Installation complete window with the Close button
    Installation finished.

Step 4 — enter the key

  1. Open Word or Excel. The Activate Office window appears.
  2. You don't have to sign in with a Microsoft account. Choose I don't want to sign in or create an account at the bottom. If you do sign in, the licence is saved to your account — that is fine too.
    Activate Office window with the link I don't want to sign in or create an account highlighted
    Signing in is optional.
  3. Enter the 25-character key from the email and click Activate Office. Accept the licence agreement.
    Field for the 25-character product key and the Activate Office button
    You can type the key with or without the dashes.

If the window doesn't appear, go to File → Account → Activate Product and enter the key there.

Step 5 — check the activation

In Word, open File → Account. Under Product Information it should say Product Activated and the name of the version, for example Microsoft Office Professional Plus 2021.

Word, File, Account: Product Activated under Product Information
This is what activated Office looks like.

The screenshots are simplified illustrations. Your windows may look slightly different depending on your version of Windows and Office, but the labels and the order of the steps are the same.

Project, Visio and Windows bundles

  • Project 2021 and Visio 2021 install the same way, each from its own .img file. If Office is already on the computer, it must be from the same generation — 2021 with 2021. What each program does is explained in our article on Visio and Project.
  • Windows + Office bundle — the email contains two keys. Activate Windows first with the Windows 11 or Windows 10 guide, then Office with this page.

If something goes wrong

  • The key is not accepted — usually another version of Office is still on the PC, or the file for a different edition was installed. All the causes are in our article on Office keys that don't work.
  • Word says "Product not activated" — see what it means and how to fix it.
  • Online activation gives an error — telephone activation is the fallback. In the activation window choose to activate by telephone, take a screenshot of the Installation ID and send it to us. We send back the confirmation code.
  • You changed the computer or motherboard — see what to do.
  • Nothing helps — email us at info@litsenzi.bg with your order number and a screenshot of the message. We help with activation free of charge, and if the key really doesn't work, you get a replacement or a refund.

Don't have a licence yet?

Office 2021 Pro Plus is the latest version, with Word, Excel, PowerPoint, Outlook, Access, Publisher and OneNote. Office 2019 and Office 2016 cost less and cover everyday work. If you also need Windows, the Windows 11 Pro + Office 2021 Pro Plus bundle costs less than two separate orders.

The key usually arrives by email within 15 minutes during working hours, together with an invoice.