Constant freezes and crashes . . . not sure what to try next

I've been having problems with my computer crashing or just freezing up when I try to watch Hulu or play facebook games full screen. That seems to be the only times it has problems. I've had it crash once while playing WOW, but that was it. Also, not sure if it is related, but even when not playing full screen, facebook games, such as farmville and frontierville, run slow. Wow and other games seem to run smoothly unless there is a high amount of action on the screen.

I've run memtest with no problems and I've made sure all programs and drivers are up to date. Could use some help with what the problem may be. Software or hardware? Thanks.

Go to search type device manager and look for any yellow warning markers
Download and run malwarebytes, a full scan after you update
Run antivirus scan
Check memory with memtest86
Make sure that you are not over heating.
Try in safe mode; report back if it works properly.
Try a clean boot
Make sure PSU is working properly
If overclocking, restore to original
Test hard drive at company website.

Check back and I will get you some links that you can use for the above
http://www.geekstogo.com/forum/topic...ing-memtest86/
http://support.microsoft.com/kb/929135
http://malwarebytes.org/
http://www.almico.com/speedfan.php

This seems like a lot, but go slow, ask questiions and you will be up and running.