Computer powers up and down repeatedly

[jimb_04]

I have an HP A6720Y desktop that worked fine until last night. The game TrackMania locked it up. I tried the windows key and Ctrl Alt Del with no avail. I left it for a few hours and when I came back it was the same so I held the power button down until it turned off. This morning it wont start. The power light comes on, the fans starts and it sounds like the HD is spinning then it shuts down and tries to start again.
I read a lot of the messages in here about the same problem. I hope someone can give me advice after knowing what happened before the trouble started.
Thanks

 

[Quadacon]

are there any beeps coming from the computer? can you get into the bios?, a little bit more info would help

 

[jimb_04]

No. No beeps. Just fans for a second or two then it stops and after a few seconds repeats.

I unplugged the HD, CD, Vid Card and all but 1 stick of RAM and the same happened. I tried swapping out the RAM sticks but didn't go through all of them.

At first I thought the game freezing was a conflict of some kind and I made damaged something by the hard reset but now I wonder if the game freeze was the sign that something failed and the hard reset didn't matter.

 

[jimb_04]

One more tying I noticed today is that with the computer plugged in the green power light on back is on but when the computer tries to reboot it blinks off then on again. It stays on until the next power up and blinks off. I don't know if that is nor.al or not.

I apologize if this is in the wrong category.