I've got a question along similar lines.
I'm about to aquire a second hard drive and I'm wanting to move Sims 2 to the second drive. I'm hoping someone more tech savvy than me tell me the easiest way to do this without starting all my families again.
Just move your My Documents folder to the new drive. Right click on My Documents, set the new disk as target and say yes when it asks you if you want to move your old documents. The game figures it out from there.