I switched mobo, cpu, and ram about a year ago and couldn't load windows XP. a quick fix for that was installing a fresh copy of windows on my spare hard drive, downloaded the drivers I needed and set my original hard drive as a slave. once I backed up the files I wanted to keep I revesed the hard drives, formatted, XP'd, and transfered files back.
I don't know if this was a one time problem or a fequent problem with mobo swaps but at least hard drives are non-volatile so trying wont erase your files(until you format).
if you want to save your programs though you might have to use a backup program if they cant be transfered.