System doesn't post

[xfire]

The system config is P-4 prescott at 2.8Ghz
Intel mobo and 300w psu(This is all I know about it)
So it was running allright but the CPU starts to get over heated. I opened it to dust it and then put it back.
I start it up and it freezes and the splash screen of Xp.
I open it tinker a bit and then it Xp starts and says it needs to scan the disk,but it freezes at 33% .
and now it doesn't post at all.
I changed the PSU and tried but it didn't work.
What could be the problem?

 

[Fitseries3]

reseat everything in the board.

 

[Namslas90]

Remove CPU heatsink, clean and reapply thermal paste, reseat heatsink, check CPU fan and try to boot.

 

[xfire]

I did remove the battery but it didn't help.
Is applying thermal paste nessacary for it to post?
The case fan and the cpu fan are running but there is no display.

 

[JoshBrunelle]

did you reseat everything as fit said? RAM, cables, psu cables?

 

[erocker]

Is applying thermal paste nessacary for it to post?

Yes. Your CPU is overheating and the system is shutting itself down.

 

[xfire]

I did reseat everything. The CPU is overheating, that's the reason I opened it to dust it but the sytem isn't even starting all it shows is the orange light.
I'll try it though.