Compaq v700 power/screen issues (power cycles)

I am working on a customer's laptop here, their story is they was playing a game and the screen went blank but the system was still on, so they did a force shutdown by holding the power button, and when they tried to turn it back on, it would power up for a few secs (no screen) and shut off. They took it to best buy and they drained the battery and checked the ram with no luck. They want $70 + repair costs to fix it if they do anything else, so they will probley say the motherboard.

Anyway, here are some of my test results:

If I power it on and tap the f10 key (guessing key for entering bios settings) it will stay on but still no video/backlight on screen or external monitor. Swapped batteries / ac power supply with my own since i have a HP that uses the same models and the same results. Also if i remove the ram completely or partly (1 stick) it still does the same thing.

While when I think i'm in the bois I try to hit Esc then enter (exit bois) and I don't notice any changes in the system (no hdd read etc).

I can't really place what exactly is wrong, I thought at first the video card died on the mobo, but since it wont even attempt to load windows or read the hard drive after the POST I'm kind of aiming at the power circut on the motherboard or possibley something else on the mobo.


Just a little background about me, I work on game systems quite often modding and fixing them. I have fixed motherboards that best buy has said was complete junk (heat sink anchor came unsoldered for northbridge). I have fixed several power jacks on laptops. I am pretty good with a soldering iron and using a heat gun (xbox 360 BGA problems).

Anyway, if anyone has anyinfo that would help me solve the issue, that would be great, the owner don't have $500 or what ever it would cost for a new motherboard.

Thanks for the help,
Cmd

 

Updates:

I took the laptop completely apart and the geek squad broke a part of the cmos battery holder so it don't keep the battery in. I dont know if this has anything todo with what happened, but i pushed it in and held it while i powered it on (with nothing connected to the mobo except power, power button, and external monitor), it powered on the same way as it was before (fan speed) then it sounded almost like it did a quick soft reboot and the fan slowed down and I actually got the boot screen from the bios, but I had no keyboard hooked up to press F10 to enter the bios.

I now know the video card works, good or not I don't know. I also replaced the CPU compound while I was inside it.

Is there anything else you guys think i could do to figure this problem out?

Thanks,
Cmd

After I shut it down and tried to turn it back on, it power cycled again.