Laptop startup problems

HP Pavillion Special Edition DV 6700 purchased summer 2007
Intel Core 2 Duo T5750 2.00 GHz
4 GB RAM
Win 7 Pro 64 bit/XP Pro 32 bit
Nvidia Gforce 8400M GS

My computer runs fine when it's on, but on occasion when I try to start it up, it will turn on for a split second and then lose power. I try again and again it turns on for a second and then loses power. I usually have to try a couple of times to get it to start. Once it's on it runs fine. Usually, the startup issues happen when I try to restart. Instead of shutting down and turning back on it simply powers down. The above scenario then plays out. Also, it will sometimes freeze at the HP splash screen. I have to hold in the button to shut down and try again when that happens. Any ideas what this could be? Does it sound like something that a reformat could fix or does it sound more like a BIOS/hardware problem? I think unfortunately it may be a hardware problem but I wanted to ask you guys to get a second opinion. I'm afraid that one day the computer may just decide to not turn on at all.

P.S. I have overclocked my graphics card. I suppose the extra heat may have fried something but I'm not sure.

Yes this loooks definitely like a hardware problem with it's startup symptoms

And your OC attempts are a clue- did the laptop get more hot since then, does the fan work louder/more often ?
With such problems you should definitely go back to standard settings of the graphics. how long did you have it like that?

From what I've seen many of these dv6000 series have problems with their BGA chips that need reballing
so maybe the additional heat you had, contributed to the problem of one of those chips on the motherboard. Or it would happen anyway

Nicely named, indeed some of those laptops have such problem "built-in" so you pay even more than thought at the beginning (if you expect long lifetime . I have one of those dead dv6000 here..

You may need to compare service prices with new motherboard (if you want to play with it , depends on your location I think.