I was playing a game on my (~2 yr old) computer a while ago when it locked up on me, and then crashed. Since then, when attempting to power on the system, one of 3 things will happen:
1) It will successfully POST, and then give me an "DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER" message.
2) It will successfully POST, and then I will boot from the dvd drive. However, the hard drive will not be detected.
3) It will power up, but the fans will remain at full power (instead of slowing down after a moment) and nothing will be sent to the monitor.
If I leave the system off for a while and try to power it on, I will consistently be able to get scenario 1 or 2 above. Once I get one of these scenarios I can leave it running seemingly for as long as I like (for example, while running memtest for hours, no problems). However, I can only get it to POST once or twice before I start getting the 3rd scenario above and have to let it sit for a while again.
An additional odd symptom: when powering the system down with the normal power button on the case, it sometimes turns itself back on shortly after (unless I flip the PSU switch of course).
Things I have tried that have not altered the symptoms:
-Running one stick of RAM or the other instead of both (also ran memtest, no errors)
-Disconnecting HDD and DVD drive from mobo/PSU, leaving only mobo, RAM, video card, PSU, CPU/heatsink inside the case, and keyboard, monitor, power cord attached outside the case.
-Plugged computer in at a different outlet that powers other computers without issues
Any help/suggestions are greatly appreciated as this is driving me crazy trying to fix this.
CPU: Intel Core2 Quad Q9450
RAM: 2x 2-gigs DDR2 800 MHz
PSU: Antec BP550 Plus (550W Continuous power)
Graphics Card: Nvidia Geforce 9800GX2