Which version of Windows? 7, Vista, 8, 10?
Start with the mouse. Disconnect the USB plug that connects your tablet to your computer then restart krita and try zooming with:
The mouse scroll wheel,
The slider at the right hand side of the status bar,
The Ctrl+ ‘+’ and Ctrl+ ‘-’ shortcuts,
Ctrl+space+ mouse left click-hold and move it up and down the canvas,
Any other zooming method I may have overlooked.
Do they all work, or not?
If not, do they all have the same problem behaviour?
If there’s some or all not working, create a new image and try the same zooming attempts on that and see if that fixes any problem.