Warchamp, the best way to do that IMO is to make two copies of your WoW directories except for the wow\DATA directory, then link the DATA directory in your 2nd account to the DATA directory in the first account. That keeps the space consumed on your hard drive to a minimum, loads faster and totally prevents them from overwriting each other's settings.

Look up NTFS Junction Points here on the forums -- there are several other threads about this. Good luck!