I'll try and add to the confusion. I'm listing things you may have already tried - ignore as you see fit.
...Restore your BIOS to defaults.
...I would start with the memory modules.
Are they matched (not mixed) speed, size, brand
If you have a min. 512MB ea. stick - test 1 at a time (proprely located if slots differ)
If you have access I would test other memory modules
...A Live CD (Linux maybe) or UBCD may help - see if it will load on your system.
If it loads you may rule out CD/DVD drive and cables???
UBCD should have a tool or 2 for CPU diagnostics
...Install an OS from another machine onto your drive.
If it installs you may rule out hard drive???
You can test the drive from this machine while your at it to rule out failure
...I don't think
all the OS discs are bad - you could rule them out.
...Also, some details about your system might be helpful.
Mobo, BIOS, CPU, RAM, Hard Disk, etc - the sound card doesn't matter - just vital statistics
