There are a lot of things that can cause freezing, from incompatible or damaged video drivers, to program conflicts or overheating.
What antivirus program are you running? McAfee has been known to be an issue for some. If you are not running one, you need to do a scan to eliminate possible infections.
Spyware that gets installed with many programs is another common source. You can run Ad-Aware to detect and remove them. Read the "getting started" and FAQ pages before running it and know how to restore from the backup it creates if that should be necessary.
http://www.lavasoftusa.com/
Reducing video driver hardware acceleration helps many with freezing problems. To do this, right click on My Computer and select Properties>Performance>Graphics.
Try sliding the acceleration position at least one notch to the left.
[I'd like to know what you have running in the background too. Do a ctrl-alt-del and list for us everything there except Explorer, systray and rnaapp (if present)]