Vista x64 Horribly Choppy and Slow

Alright So I just recently built a new Machine with vista 64 bit home
premium and I'm having all kinds of speed issues. Videos are just
outrageously choppy and browsing around on mozilla gives me a few hang
ups here and there. I'm pretty sure I have everything updated too,
including graphic and audio drivers.

AMD Phenom 9950 X4 2.82 GHz
4 GB G-Skill Ram (2 X 2GB)
ATI Radeon HD 4870 512MB
Sound Blaster Audigy 2
1 TB Western Digital Caviar
Gigabyte GA-MA 790GP-DS4H Mobo

Not sure if this matters but Windows Experience Index is 5.6
(Everything is 5.9 except for the hard drive which was 5.6)

Games Run Great including Oblivion without choppiness, But just about
everything I do on vista is killing me and horribly choppy.