It just depends on how much of a problem it is and how much time you want to spend trying to figure it out.
Sometimes it just comes down to a bad registry entry, bad link to a DLL, or a corrupt file somewhere.
I have reformatted drives on many occasions for similar reasons as you have, 99% of the time that fixes the problem.
At least that way I know that I will spend 'X' number of hours installing software are restoring backups, but I know that there will be an end and the results will be good.
I'm not saying that it is the only option, just that it is an option.