Take out the mouse ball and clean it.
Or is it an optical mouse?
Mice are cheap always have a spare.
easy to troubleshoot if you have a spare.
Is it USB or is it PS2?
If you think it is a software problem, go to control panel/system/hardware/device manager/Look at mice and other pointing devices.
Click the + box next to mice and see if there is a yellow exclamation mark.
If there is remove the device/reboot and Windows will reinstall a new mouse driver.
If it doesn't, the port you have your mouse plugged into is wacked out, so change ports.
Hope this helps..............
