Multiple possible points of failure...which one?

I have an older desktop here (Compaq I think). The hard drive is definitely fubared.

The strange part is it has only successfully powered on once (when the drive was confirmed as screwed). After the initial power-on, a "coworker" took a fullsize vacuum to the thing, and that was when it wouldn't turn on anymore. This shop doesn't seem to have a multimeter to let me check the PSU (although it is choked with dust). The case panel connections seem solid, I can't get the front bezel off to check them further for loose wires.

Any ideas? I know the primary IDE drive has failed (I'm working on getting a new one in, ideally I'd like to install an OS using an external drive before I put it into the rig), but is there anything besides the PSU I should check at this point?

If it's not working now, I bet it got an ESD shock,

Vaccums create huge amounts of static electricity.

shoulda used a can of compressed air...cause at this point there is no telling...

Now a second computer on the same bench is no-boot, everything here in the shop is running open (no side panels on anything). There's a LOT of dust in the place. I've ruled out the power outlet as the monitor plugged into it works...this rig is also clogged with dust (the only other person here is the same one who took a vacuum to the other machine, so I'm not sure I want to let her near it; there is no compressed air to be had). No spare parts to be had for testing anything either (well, there are parts, but they're for sale...not even a barebones test bench)

There are two boxen on the floor here that are known good (clients' rigs that I know I was the only person to touch them)...I was considering using one of them to download needed updates for the nonworking one, but if it won't even power on...hell, either way I need a computer to do the webpage work he wants and I know the rig is clean (I can run it through some further tests anyhoo).

Dayum, my chaotic "repair corner" in my apartment is better set up than this shop (the computer I'm using now for net access is a POS laptop in the back corner with a dodgy keyboard; the computer at the front desk is being monopolized by the girl who thinks I know nothing).