PC wont post

[NeptuneUK]

not PSU. got a new one for a computer that i built up. The PC wont post. it had a cheapo 400W PSU in it. got a 450W PSU from local PC shop and PC worked.
now its doing the same thing. it wont POST til you keep restarting it. its a low/mid end PC

Jetway 915 intel chipset mobo
Celeron 2.8ghz
Radeon X700 256mb
1Gb corsair value DDR2 ram
60gb HDD


450W is more than adeqaue for this PC

 

[NeptuneUK]

5 day bump!! not been able to solve it.

 

[NeptuneUK]

if it was being shorted it wudnt work to begin with, right? no? if u keep restarting it it turns on. hmm.
its a 20pin connector in a 24pin board.