Custom built machine won't start

[little a]

hello all

we've had an old custom built machine running as our media center for some time and it was working fine until a few days ago. first starting became a problem: push the ON button and it would take 2 or 3 attempts until it cycled through normally (when it didn't the power supply would go on alone as if there was no motherboard/HD connected)

yesterday it stopped turning on altogether. the ON button by itself (i.e. pushing and releasing as one would do normally) does nothing. if i hold the power button down, it begins to start normally (i.e. fans spin and the HD light goes on) but it then dies.

my original thought was that the power supply was bad and i tried swapping in an older (working) unit but that had no effect.

any ideas? thanks folks

 

[McFurious]

What are the specs on the new unit? Is the power supply strong enough for what is running?

 

[little a]

yes, it's strong enough.

it's a pretty old Pentium D processor, and the power supply is more than plenty. ran fine for more than two years