Ok I have been using windows blinds and firefox for along time now and have never had a problem. I just recently used this theme Link

Now after using this theme and browsing the web with firefox I notcied that only on some sites, such as ones running phpBB forum software that my firefox makes my screen start lagging badly. When I change the theme everything works 100% again.

Now I know my computer can handle windowsblinds. My specs are as follows:

AMD Athlon 64 3000+ 2.0GHz
Asus K8V
ATI X800XT
1 Gig Kingston Hyper X
Dual SATA Seagate 120GB HDD's (Running in Raid 0)
500 WATT Ultra X-Connect Power Supply