Trouble with a buddies pc i built

[wilke41]

my buddy wanted a pc more like mine. so we got on tigerdirect and ordered parts. as follows:
Gigabyte MA785GM-US2H motherboard
Athlon II 240 am3 proc
PNY DDR2 800MHZ ram
and we used his old HDD and psw

we then installed windows xp got his dual displays setup, everything worked. then i opened my big mouth about a RAID setup and windows 7 64bit and taking full advantage of his 4 gigs of ram and open mouth insert foot..... now he owns 2 1tb caviar HDDs and a full license of win7 home premium and my tv tuner card and everything runs slooowww. number one i updated the bios to the latest version, all his hardware has 64 bit drivers installed from manufacturer. ive got him in a raid1 setup( or whichever raid mode is the mirrored array). win7 takes forever to load... as in "verifying DMI pool" then windows logo, except no windows logo, the video drops out (as-per the display reading "no input") and it stays like that for about 2 full minutes then loads the login screen. full screen video lags a bit in media center. he using the onboard video with a full 512 MB deidcated in the bios. and his mouse acts funny... lol this build went terribly... o and i tried booting on only one hdd non-raid after updating the bios with the same result.

any help, recommendations, criticism ( constructive or not, I'm tough , or basic insights are appreciated and most likely well deserved