is it a USB mouse or PS/2 ?
does it work booting in Safe Mode?
1. either way, open up Device Manager (Win-Key + R, type 'devmgmt.msc')
2. hit tab
3. arrow down to Mice & Pointing devices
4. hit the right arrow button
5. press down arrow
6. assuming you now have your mouse name selected, hit Alt-A
7. scroll down to 'Uninstall' and press enter
8. unplug your mouse
8. Reboot your machine
9. once the desktop is fully loaded, plug the mouse back in (if its USB)..
note: if its PS/2, then you will have to plug it back in after you shut down and the power is off, (before you computer reboots and hits the bios)
at that point, the mouse should get re-installed... and hopefully start working again.
also might want to add, what kind of mouse is it?