No lights, No display but powered on

[Wimukthi]

My PC suddenly stopped working while in use... The screen went black and the "check video cable " sign came up. This has happened before and started a few months back and whenever it happened I had to take the rams out and fix them again for it to start working. I had done a minor bit of CPU over clocking a few years ago without increasing power to the CPU and whenever these crashes happen the bios screen says over clock failed. So I have to over clock again but I know there isn't any problem with the over clocked CPU because I have been using it for quite a long time without an issue. This time however the removing ram technique didn't work.. When I power it on the system starts up, fans spinning hard disks making the usual hum, but there is no display and the usual power and disk lights on the case don't work either. Also a weird thing is that my VGA fan starts off at a hundred percent when i start now. Earlier I had increased the fan speed using evga precision and the fan goes 100% only when windows starts up but now from the boot itself the fan is going full blast. I have tried the usual diagnostics, there are no beeps when the rams are not fixed, the VGA ( nvidia gts 250) fan is full blast even when I remove the external 6 pin power cable to it. I have tried an old VGA and the built in one but still no change. I cleared the CMOS. I did notice that there is an unusually high amount of electric charge on the case though, it sent sparks off when I accidentally brushed the VGA cable. So I removed it from the ups and the mains, got a new power chord and socket and plugged it and the sparks are gone but the computer is still the same.

EDIT

The specs are as follows
Intel core2duo e4500 2.2 over clocked to 2.7
3gigs ram
Nvidia g force gts250
Biostar g31m+ motherboard
Some generic Chinese 500w PSU

The PC is at least 5 years old now.


EDIT2

It started up and lasted for about 3mins and even loaded up windows but then turned off again.... I also noticed that the bios stated the CPU as 2.93ghz whereas it should be 2.75. I didn't do that so something is wrong there

 

[rwinches]

That sparks thing usually means a shorted wire somewhere many times a fan wire is in contact with a heatsink and the insulation melts. So give a good look see.
It seems like some PS rails are working but not all so you get this partial start up.

You really need to include a system description here as it avoids 20 questions.