Vista - Vista 64 keeps temporarily freezing

It freezes a lot on youtube and sometimes in game,it seems to get better the longer the pc is on.I have a quad boot set up with xp32,vista ultimate 32 and 2x vista ultimate 64.It does not freeze on any other boot so i asume it must be software on this one,how do i find out whats causing it?

Thanks.

Intel® Core™2 Quad Extreme QX9650 Processor (3.0GHz, 12MB Cache, 1333MHz)
Vista Ultimate Edition 64 bit with Service Pack 1
XP32 bit,vista ultimate 32/64 bit quad boot
Coolermaster Cosmos S Ultra Performance Aluminium Chassis with 1250W PSU
Cooling Pack for COSMOS S Chassis ( 5 LED 120mm fans)
Performance Pack - OCZ Vendetta Heat pipe quiet cooling
PCI-Express Mainboard - SLi nForce 780i SLi - Intel Core2Duo/Quad Core - ATX
8GB DDR2 800MHz Memory (4 x 2GB)
2 x 1000GB Serial ATA 2 Hard Drive with 32MB Buffer (2TB Total)
Blu-ray ROM Player Dual layer DVD Writer 24 x CD Writer
Super Format 20x Dual Layer DVD Writer +R/-R/RW/RAM
2x GTX260
28" Widescreen LCD TFT Digital Display with internal speakers (DVI, 3ms)
Creative Labs Sound Blaster X-Fi Xtreme Gamer Sound Card