Time Machine Migration Assistant Hanging

[ifilm4life81321]

I decided to take a risk with my iMac and do an erase and install with Leopard, the version of OS X it's been running for years now. The computer was running very slow. The reinstall went fine- migration assistent got me started transferring my information from my Time Machine external USB 2.0 hard drive. It said it was just over 200 GB of information. That proceeded fine until it reached the "Less than one minute remaining" mark. It's been sitting here for over 12 hours in the "transferring files to support applications" process. What should I do? Is it alright for me to manually turn off the computer and re-boot? There is no cancel button or anything. I do get the pleasant clunking sound when I hit enter.