a7v8x-x athlon xp 2600 installation problems

i've checked around and i couldn't find an answer to my problem arond here even though i tried a few things that were suggested.... here is what is going on... computer boots up then when it gets to boot up the os it just hangs at the dos screen without ever getting into windows... i have tried to reformat the drive with windows xp on another machine, with the windows 98 bootup disk, martigion magic windows xp installation partition.... i have also tried 4 video cards.... 2 pci and 2 agp.... i have tried installating windows xp but i never get past the first step when it is still in dos mode.... windows 98 i get to the running windows for the first time screen and then it freezes and then when i reboot it doesn't even show the windows 98 screen... but when i put the very same hard drive into another machine windows 98 boots right up....i have also tried the many diffferent settings for the cpu that i have seen around the board.... i have tried 12.5 *166 with the ram set at auto and also to 333... i have also tried the auto setting for 1.6ghz.... i have also tried 12.5* 133...and the auto setting for both 2ghz and the auto setting for the ram.... nothing seems to be working... i have also tried different hard drives....the power supply is a 400w so i belive that is more then enough power considering i have also tried to unplugg everything but the hard drive and it still doesn't boot up... i'm fresh out of ideas so i'll pretty much try anything that anyone could suggest... thank you for any help

....I've had the same problem before. Turns out my motherboard was faulty and i had to get another. HAs it ever ran Windows XP and/or 98?

Your memory can be having errors. Have you tried Memtest86?