How can I tell if my MB is bad?

[Stellar]

I have an Abit BX6r2, and have recently encountered a multitude of problems with it. It started with my sound card intermittently ceasing to work, I had to reboot a couple times to get it to work whenever it would fail. I then installed a network card, and was unable to get the network card to work properly, though it did work in another computer. Running a diagnostic problem on the card, it intermittently said the card passed tests, then would run it again and it would say it had failed the same test. I flashed the BIOS hoping to solve the problem, then was unable to get my OS to boot on my Quantum LCT08 HDD. I ended up reformatting my hdd, and still was unable to get Windows to install on it, so installed Windows on an old hard drive (had actually done this prior to reformatting other drive and backed up files). I still was unable to get Windows to install, or programs to run on the Quantum drive. My brother installed the drive on his (w/ a BH6 MB I believe) and the drive worked fine. I continue to have intermittent problems while booting with the older drive, and the network card still doesn't seem to be working properly. I think the MB itself is probably the cause of all or most of these problems, and was wondering--how I can test its integrity?