If you want to pvp in av/wg or run around dalaran for 5 I suggest these basic specs...

2.8+ ghz quad core
6gb ram
64bit os
1gb mem video card
2 screens

You can get by with less in instances and non-massively populated areas.

I'm not sure how much resources fraps takes but I dont think it's that much. It didn't seem to affect my performance much.

Also there is a hardware forum you should check out...this should have been posted in there.