Can I do this from an install though? Or should I use a LiveCD? The drives in her ewont boot at this point.
The install DVD will let you boot to a "rescue" mode, instead of typing "linux". Once in that mode, skip net and install scan. Then when you drop in to a shell, go into parted. You are installing to sda IIRC? Try:
`parted -s /dev/sda -- mklabel msdos`
Me thinks, as your system is not functioning and I *assume* no data of value on any of the discs, you sure can't make it worse:)