No boot, cpu still running arrgh

[flashbang333]

I disassembled my old pc (7 yrs old) and cleaned the case and put it back and ever since, it hasn't booted.
I don't know the mobo no. since I lost the manual.

The problem is that everything in the case keeps running (it seems to) but nothing is displayed on the screen.
I tried all the tricks, checked the ram etc...

The pc has a graphics card as well as internal vga.I tried both.I even tried all the bios cleaning tips like removing the battery for 10 min, changing jumpers below it etc.yet nothing happens.

Also I removed the both the RAM chips and everything else but cpu psu and mobo. and booted and there were no beeps !!!!

Specs
Intel P4 1.7 Ghz
DVD r
HDD 40 GB Seagate
5200Fx nvidia graphics card
768MB DDR1 ram (256 X1 and 512 X1)

 

[Proximon]

And is there a speaker on the MB or connected to it?

 

[flashbang333]

Yes actually there is an onboard speaker (little small black one) and a big one on the case.
Both connected.

 

[Proximon]

Sounds like the board is toast then.

 

[aford10]

Does the mobo have a 4 pin CPU power? If yes, make sure it's plugged in all the way.

 

[flashbang333]

, first it was disconnected but i connected it but no effect.

 

[aford10]

Any fans spinning?

 

[flashbang333]

Yup, the psu and cpu fan are running

 

[aford10]

I'd try a different PSU.

 

[flashbang333]

Sorry, can't buy or borrow a new psu.

The CD drive, DVD drive start running and open too, so I guess the psu isn't dead .

 

[Proximon]

The presence of power does not mean the power is stable enough to run the computer. My best guess is still the board though.

 

[aford10]

Those are the symptoms you would get if the 4 pin cpu power wasn't plugged in. So, the port (mobo) or power cable (PSU) could be bad.

 

[flashbang333]

sorry for being clumsy in my replies.

How can I check which one is bad ??

 

[aford10]

Borrow a PSU and test it on your system.