BleepingComputer.com: HP 725n won't post after installing new heatsink & fan

I've been trying to keep an old HP 725n desktop going.

First I added some memory, have 1 gig (max for this motherboard).
I replaced the PSU and added an AGP graphics card a while back, no problems.
Also had to replace the CD/DVD drive, also with no problems.

I was thinking of turning it into a server, and noticed the CPU was running very warm, so I ordered a new CPU Heatsink & fan.
I installed them yesterday, it was a real tight fit getting the heatsink to snap on over the CPU but I eventually got it to lock.
Had to use a lot of pressure to get it to latch.

Put it all back together & it worked fine last night, the CPU temp dropped by about 9 degrees C.

But this a.m. I go to fire it up & have no video signal from the video card; I switch over to the back to the graphics off the motherboard & have a signal
so I open it up & reseat the video card & I get a signal from it.

So the next time I try to boot up nothing - no post, no beeps.
The fans all come on, & the CD/DVD spins so I guess there's power from the PSU.

Could I have damaged the Motherboard when installing the heatsink maybe?
How can I troubleshoot this?

Any advice is welcome...

Thanks
BT.

It sounds like the PC is defaulting to the on board (on mobo) video.

With the computer off and the monitor plugged into the mobo go into BIOS. There should be a setting to either disable the on board to choose the AGP slot for it to use for video.

Save and exit settings. Turn off the PC.

Plug the monitor into the new card and restart the PC.

Let us know if this works.

Thanks Thunder - that did fix it, at least I was able to boot up in safe mode & then do a system restore.
since that things seem to be working normally.
I appreciate the help.
BT

Curious why a system restore was necessary.

But if everything is working and you are happy.......

Is it an Nvidia card by chance?