I have a Dimension C521 running Vista. First, upon boot the system beeped and I think the fan would start blowing loudly, but no video would appear on the monitor. I would hold the power button down to shut down the computer, then press it again. After repeating this several times, the message "Diskette drive 0 seek failure" would appear. If I pressed the enter key, I could get to Vista. I tried changed the BIOS to disable the floppy diskette, since I don't have one, and it seemed to work if I restarted rather than shutdown. Recently, I am not getting any video on boot after many tries. I've tried reinstalling the RAM cards, no luck. I have a suspicion I was hit by a virus. Thanks in advance for any assistance.