PC starts to boot, shuts down, and restarts

[MadMontie1]

I've got an older Dell Dimension 4550 (likely almost 10 years old)

Without any advance warnings, computer has died.
Pressing the power button results in computer starting for about 3 seconds, shutting down, then restarting on it own and continually running, no additional signs of startup.

Nothing ever appears on the monitor. The "no signal" message does dissapear when plugged into the video card, but remains blank.

Have already ruled out the power supply (purchased new, same thing) and monitor (hooked it up to another computer.

Removed and re-seated video card and all ram sticks. Leads me to believe its the video card, but when I remove the card all together, the same exact boot scenario occurs.

Removed the hard drive and all unnecessary peripherals, same thing.

So, any bets on video card vs motherboard? If motherboard was bad, would anything happen when I pushed the power button?

Thanks in advance folks.

-Montie

[mechbas]

If possible you can try the graphics adapter (video card) in another machine but that will probably not make any difference either. Seems your system board has permanently gone bye-bye.
"would anything happen when I pushed the power button?" (short answer, under the circumstances) No.

[cguan_77]

bump to same problem before, but solution i did was quite simple. you might not believe, but just try changing your CMOS batt, check if you had the luck.

Good luck!