Hi Dagurl92,
Do you have a USB mouse from another computer or that you can borrow briefly from a friend or anyone? I'd like to see if another mouse that we know works fine works OK on your computer or if you have the same problems. I realize USB is different than built-in, but it's still an excellent test and a very good thing to know. It narrows down the possible causes possibly more than anything else suggested.
Do you know when this problem began? Try a System Restore to a point in time BEFORE the problem began. Here's the procedure: http://www.vistax64.com/tutorials/76905-system-restore-how.html. Be sure to check the box to show more than 5 days of restore points. If the first attempt fails, then try an earlier point or two. NOTE: You will have to re-install any software and updates you installed between now and the restore point, but you can use Windows Update for the updates.
If the mouse is built-in to your computer, your best bet is to go to the computer manufacturer's web site and download the most updated drivers, firmware, and/or software applicable to the computer and your operating system. Make absolutely sure you get the correct downloads as the wrong ones can make things worse.
What is the manufacturer, make, and precise model of your computer - this will help us confirm the downloads and check troubleshooting guidelines and any available manuals on your system (AND is also critical if we're to help you any further)? That way you are certain they are the proper programs (and the other sites may only contain drivers whereas your mouse may also require firmware and/or software as well - which you'll discover on the website). Keep in mind that just because Device Manager says it is functioning properly does not guarantee that is the case - the problem may be too subtle for Device Manager to detect but enough to cause your mouse to have problems. It's best to update (even if it is the same version) just to be sure and rule this out as the cause.
If that doesn't work, try a clean boot http://support.microsoft.com/kb/929135. If the problem goes away then it's just a matter of tracking down the culprit causing the problem. Follow the procedures in the article. Once found, delete, remove, deactivate, or uninstall it. Once done be sure to reset Vista back to normal status as explained in the procedures. If the problem occurs in clean mode then just restore the system to normal status and reboot - this solution is not going to work.
Boot into Safe mode with networking and see if the problem occurs there. Either result helps us narrow down the search for the cause.
I hope this helps. Please update us on what happened with each procedure you tried and which, in any, you skipped (so we'll know what we can eliminate as causes and refocus on what remains). If the problem persists, there are other options we can try - though they become less likely and/or more dramatic as we proceed.
I don't suppose the computer is still under warranty - no, that would be too much to hope for.
Do you have or can you borrow a Vista Installation Disk of the same bit-size (it does not need to be the same version)? We don't need it yet - but it may come in handy later.
Good luck!
