Self-Resetting BIOS

Hello, Sorry I''ve been asking so many computer harware related questions, but I guess it''s better than those oh so many crap postings... Anyway, I wanted to set my "Graphics Aperature Size" and stuff like that in the BIOS, but when I restart the computer, (by pressing F10 which saves and exits the BIOS), It is always reset back to the defaults. Other settings like boot drive order stay the way I set them. What would cause this? thanx for any help! tazzel3d ~ dwiel