Vista re-install crash may have killed my MB

Ok, bear with me cus this could take a while.

I cleaned an old computer after putting in a new HDD. I re-placed the thermal compound on the heatsink and air-blasted all of the dust out of the case. The PC had been running fine beforehand and I was going to do a fresh install for a friend.

I set it back up to the monitor, mouse etc and booted the computer. I put the Vista install DVD in and proceeded to pick the install. I left the computer and came back 5 mins later. The screen was black and the computer seemed idle. I left it another 5 minutes and after nothing I reset the computer. The POST came up and I let it try and boot from HDD. Files were missing. I thought, that's fine i'll just format and try again. Tried to boot from the disc to format the HDD. The DVD booted then crashed before even loading the keyboard settings. After resetting the computer again, it no longer gives out any signal.

Now when I turn the computer on I get no signal to the monitor. It also doesn't shut down using the power button on the front of the case (like it used to). I'm afraid I may have damaged the MB =(

Any help or advice would be MUCH appreciated thanks!

Ben

*Ps I left the side of the case on. When I 1st built the computer I left it on, but int he coming yrs, due to age and dust and whatnot, the computer would crash when the side was left on. After I cleaned the computer, i attempted all of this with the case side ON the case.