Laptop troubleshooting forum: HP Pavilion dv6000 boot up issue

I have a HP Pavilion dv6000 running Vista with 3 gigs ram that is about 6 years old. One morning I went to turn it on and apparently it had downloaded an update file from HP and of course I had to wait for it to install the updates then automatically restart. After the installation was complete it shut down. After a few moments of waiting for the restart to occur nothing happened so I hit the power button. It turned on for a second or two then shut down and nothing comes up on the screen. It then starts to repeatedly cycle on and off again just for seconds at a time.

At the time I knew I had an old battery that wasn't holding a charge for more than 20-30 minutes but I always had the power cord plugged in so I didn't think it was that. I tried pressing the escape key as soon as the power came on and the power did stay on this time but again the screen stays black (same results when hitting F keys. I've tried all of them!). The CPU fan runs as does the dvd drive motor. all the lights at the top of the keyboard light up and the two lights at the bottom indicating the power and on/off light up but the hard drive light does not. I was told that it may be the battery so I removed and reinstalled it to no avail. I even bought a new battery but this didn't change anything. I don't have an external monitor or a cable to plug into my new laptop, if that is even possible, so I can't see if there is anything coming up when I hit excape.

I've since gotten a new Laptop so I'm just wanting to recover the HP to use as a second when my wife wants to use it at the same time. I've read other posts indicating that it may be the graphics or mother board and hope that it's not the case but fear the worst.

To recap when I turn the power on all the lights come on but the hard drive light for just a second or two then it shuts down then just cycles on and off repeatedly. The screen stays black as if no power was getting to it. To stop this I've held the power button down until it stops. I've tried hitting the escape and F keys immediately after pushing the power button and it stays powered on but the screen remains black and all the lights come on but the hard drive light on the bottom left. I've removed and reinstalled the battery, the old one and the new one but nothing has worked.

Any advise is appreciated!