No, you wont experience any problems. That is actually what I am planning to do. I am buying a 120+gig 7200 RPM 8mb cache hard drive for my computer. It will go in my computer. I will take out the current drive, which is a 40 gig and stick it into an external firewire case. Then I will have a 120gig internal drive, and two external 40 gigs for back up. 🙂