Installing and activating Windows 10

Windows 10 still runs and activates normally. Microsoft's free support ended in October 2025, and Extended Security Updates (ESU) for home users ended in October 2026, so the system no longer receives security fixes. If your computer doesn't meet the Windows 11 requirements, Windows 10 is still a sensible choice. What the end of support means in practice is explained in a separate article.

If Windows 10 is already installed

  1. Open Settings → Update & Security → Activation.
  2. Choose Change product key.
    Windows 10 Settings, Activation: the Change product key link
    The key is changed in Settings → Update & Security → Activation.
  3. Enter the 25-character key from the email, click Next and then Activate.
    Product key window with the Next button
    You can type the key with or without the dashes.

Check: the same screen should say that Windows is activated. For a second check, press Windows + R, type slmgr /xpr and press Enter: the message should say the machine is permanently activated. More ways to check are in the article on checking your licence.

If you are installing Windows 10 from scratch

Before you start

  • A USB stick of at least 8 GB. Its contents will be erased, so move your files off it first.
  • A backup of your important files: a clean install erases everything on the drive.
  • Windows 10 doesn't require TPM 2.0, so it runs on older computers too.

Step 1 — download Microsoft's tool

Open the official Microsoft page for Windows 10 and start the download in the section on creating installation media. This downloads Media Creation Tool.

Don't download Windows from other websites. The installation files are free and come straight from Microsoft — you only pay for the licence.

Step 2 — make a bootable USB stick

  1. Plug in the USB stick, run Media Creation Tool and accept the terms.
  2. Choose Create installation media (USB flash drive, DVD, or ISO file) for another PC — even if you are installing on the same computer.
    Windows 10 Media Creation Tool: Create installation media selected
    This option prepares a USB stick for installation.
  3. Leave the language and edition as suggested, unless you need a different language.
  4. Choose USB flash drive, click Next and select the stick.
    Media Creation Tool: USB flash drive selected
    Choose the USB stick as the media.
  5. Wait until Windows 10 is downloaded and the stick is ready.

If Media Creation Tool won't run, download the ISO file from the same page and make the stick with the free Rufus program.

Step 3 — boot the computer from the USB stick

  1. Leave the stick plugged in and restart the computer.
  2. Straight after it powers on, press the boot menu key several times. It is usually F12, F11, F9, F8 or Esc, depending on the make.
  3. Choose the USB stick from the list.
    Boot menu with the USB stick highlighted
    The menu looks different on every make, but the USB stick is always in the list.

If the computer still loads the old Windows, go into the BIOS/UEFI settings (usually with F2 or Del) and put the USB stick first in the boot order.

Step 4 — install

  1. Choose your language and keyboard, click Next and then Install now.
  2. Enter the product key, or choose I don't have a product key and enter it after the installation. In that case, choose the edition your key is for (Home or Pro).
  3. Accept the licence terms and choose the second option, Custom: Install Windows only (advanced). It performs a clean install.
    Windows 10 Setup: Custom installation selected
    The second option performs a clean install.
  4. Choose the drive and click Next. The computer will restart several times — that is normal.

If you want to keep your files and programs, don't boot from the USB stick. Run Media Creation Tool in your working Windows and choose Upgrade this PC now.

Step 5 — activate

If you entered the key during installation, Windows activates itself as soon as it connects to the internet. If you didn't, go back to the start of this page.

The screenshots are simplified illustrations. Your windows may look slightly different, but the labels and the order of the steps are the same.

If something goes wrong

  • The key is not accepted — usually the edition doesn't match: a Home key can't activate Pro. The other causes are collected in our article on activation errors.
  • Windows deactivates after a hardware change — that is normal, because activation is tied to the motherboard. The fix is in the guide to transferring a licence.
  • 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?

Windows 10 Pro adds BitLocker, Remote Desktop and domain join to what Windows 10 Home offers. If your computer meets the Windows 11 requirements, also see our comparison of the two systems — Windows 11 still receives security fixes. If you also need Office, the Windows 10 Pro + Office 2016 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.