windows 7 keeps freezing

hey everyone,

 i've been having a problem with my newly built computer freezing on me. it could happen at any time, but it usually happens when i'm playing a game in windowed mode and trying to multi-task by opening up firefox or MSN chat. it also happens occasionally when i'm just browsing youtube. when it freezes, the screen will always go black and/or it will have colored lines that look like | | | | | all over the screen. i checked my cpu and gpu temperature which both seem to be fine. while playing games, both stay under 50. i don't believe it's a virus because i had this issue about the 2nd day after building the computer, although it seems like it's been freezing more often now.


edit----

specs: ASUS m4a79xtd evo motherboard, amd phenom II x4 955 processor, ATI radeon hd 5700 series, corsair xms3 ddr3 4g, windows 7 64bit

please let me know if there is any other information anyone would like me to post. any help would be much appreciated.

This sounds like an issue with the graphics card or it's drivers. try updating and/or rolling back the drivers and if that fails you may need to replace the card.