Hard Drive Issue.

Hello all. First post, so hope I'm in the right area :) . My Tivo had a 320gig hard drive in it so I wanted to put a bigger hard drive in. I connected both drives to my computer and opened up WINMFS. I am using Windows 7 and a window popped up and I clicked something regarding the Tivo drive (MBR something I think). Within WINMFS I can see both drives, but the Tivo drive says "UNALLOCATED" and I can't see anything on it. Is there a way to retrieve my Tivo Image to put on new hard drive or can I download it? Thank you.

Are you using WinMFS version 9.3g (for Australia/NZ)?
Also did you run it as Administrator?