Problem with system

[LukasNT]

Hello, so i don't know is anyone still famillar with late 2000s systems. So i decided to give my 2008 pc an upgrade. It had Core 2 duo E8200, 2gb of ddr2, HD3870 OC gpu and 400w psu. So i try to give the parts which dont need psu upgrade. And i gave the first upgrade: Core 2 quad q9650. So and i needed a gpu upgrade, because i thought it was fried, but i gave an old gpu a chance to work so i installed newest drivers possible and i got it working. That was a week ago. Now i want to install windows 7 from xp, but i wanted to format it so i had to take all photos and stuff out. So i booted it and firstly tried to play some spintires, but it crashed and gave 720p res. on screen and artifacts. So i'm back at stage one like before installed drivers. Also when i tried searching for files in that "search" and i started, but windows explorer just send crash reports, well windows did fine, but if you press "dont send" it i'll crash windows and stuff. So is it again gpu or else? Also when i put new cpu it showed on the properties Pentium III Xeon, but on cpu z fine. I'll apreciate any help. Sorry for not that good english.