Here are some steps you can try to fix a sideways screen on your Windows computer:

1. Right-click on the desktop and select Display settings.
2. Choose a screen to fix if you have multiple monitors attached.
3. Select Landscape from the orientation menu.
4. Click Apply (or OK).
5. Click Keep Changes when prompted.

Alternatively, you can use these common keyboard shortcut combinations to rotate the Windows screen to normal:
- CTRL+ALT+Up Arrow
- CTRL+ALT+Down Arrow
- CTRL+Alt+Left Arrow
- CTRL+Alt+Right Arrow