you could try running 'Scandisk' and 'Defrag',in ME I think they can be found in Start>Programs>system tools.
If you run them, make sure any screen saver and virus checker you have is turned off first.
Also make sure your virus checker is uptodate and run it after Scandisk and Defrag. It is always a good idea to keep the virus checker uptodate.
Have you downloaded anything onto your PC before it started freezing? If so it could be this that is causing the problem. If possible uninstall it.
You also have an option of using the 'restore point' if all else fails. This again can be found in start>programs>system tools> restore point. It enables you to go back to a time when the PC was working properly.
This option has its 'problems' 1. it is not a fix as such. 2. you will loose any and all work etc that has been put on the PC since the restore date.
You may find that no restore points have been set or they have been set some time ago if you have not been making them yourself....so be warned.