you say you just installed your mobo! updating bios can sometimes sort out faults even if just small ones.reason i said that were i had instabilty problems when i first put my abit is-7e in that were fixed with a bios update.
and secondly you did not say it were in the smartgart that were resetting,looked more like you stated it were your bios resetting.
have a look at smartgart in windows to see what that shows up 4x or 8x?
"It wont stay 8X in my control panel" have you installed the newest chipset drivers for the nf7-s
nforce 2 for xp
nforce 2 98/me