Jason,
As the lid is off, go for the minimum system approach that Richard suggests. But before an reinstall try low level formatting the drive with tools from the drive manufacturer (I can't remember who your drive was from but post make and model for it and i'll have a look for the tools for you.) then going for a windows re install.
At least if you can get something up and running you will be confident that it is not a MoBo problem before unpacking the new drive.
With regards to doing that minum rebuild you could do it in stages, but it is a lot more work. Depends what you have to boot from e.g. cd / floppy but build a bit, boot a bit build a bit and so on would let you only add components to a known good base and lets you have more of a chance of spotting the problem.
Assuming you have a CD you can boot form start with just:
Mobo/CPU (Set the BIOS to boot from the optical drive)
RAM
Optical Drive
Keyboard
Monitor
If it boots e.g to a DOS prompt, run memory checks, check CPU temp. and performance.
Then add the HDD, check in the BIOS that the drive reports the right size etc.
Then see if the system boots and you can change to the HDD.
If that works i'd format the drive at that point but not put windows on it.
Then add everything else the floppy drive, mouse, tv-card etc. You could add them all one by one before the reinstall if you spot no problems at all before this stage, but i'd be surprised if any of them are causing the problem.
Then when your new drive arrives, pop it in and make that the main drive!
Memetic