Will not boot with a particular monitor?

Hi all,
I'm in need of a bit of help ; )
One of my friends has a mesh PC running Win 98.
It has been working fine until about 3 weeks ago when he phoned me up and asked me to take a look.
It was only booting in safe mode and I could not seem to fix it there. I took it home and discovered that it was built using a RAID mobo, and both CD's were on the raid adapter, once i had reconfigured these I gained access to the OS, discovered that the graphics drivers needed to be reinstalled and then discovered that the heat sink had fallen off the graphics card cpu. I stuck it back on, tested it overnight, and all seemed fine.
I gave him the PC back and it worked for 3 weeks but I got another call yesterday, I picked up the tower, brought it back to my house and it worked fine. but when I took it back it wouldn't boot up normally, brought it back to mine - worked fine???
The graphics card is a GeForce2 MX/MX400
Can anyone give me some advice on what may be stopping this machine booting up when connected to their monitor
but works fine on my two?

Many thanks

Spotta

 

You/he may also be a victim of coincidence here as well. If the heat sink had fallen of the graphics card then chances are that the GPU is damaged due to heat stress, and the coincidence maybe the fact that the GPU is cooling down and happining to work when the PC is at your place. You could spray some electronic (non conductive) freeze spray in the graphics GPU when in fault mode and observe. You may need to reboot though to force a change?
But as Pete suggests, could be an intermittent monitor as well.

 

Thank you both for the advice.
I removed and reinstalled the gfx drivers
set it to 800x600 low colour
took it back and upped the settings while it was on his monitor and it worked fine.

Spotta