All right, me next!
Do A Disk Clean Up. Get ride of those old temporary files and all those files that you don't need anymore. This really works for me.
To Access Disk Cleanup, do the following:
Click Start then go to All Programs then click on Accessories. After that, choose System Tools then click on Disk Clean Up
Now when you reach disk clean up, there is a list of objects that need to be checked off. The things that you will check off will be the things that you need to be cleaned off. If you want to be safe about the whole thing, you can just check these:
Temporary Internet Files
Offline Webpages
Microsoft Office Temporary Files
Microsoft Error Reporting Files
Temporary Files
Compress Old Files