1. Remove the old drive from the MagicTV, complete with recorded programs.
2. Insert the new bigger drive, and run through the rescue procedure.
3. Remove the new drive and mount both the new and old MagicTV drives in a PC together.
4. Insert a Linux CD and boot to that. I just ran it in demo mode directly from the CD.
5. Log in as root and then copy the data from the two partitions on the old drive to the corresponding partitions on the new drive.
6. Reinstall the new drive into the MagicTV.
It now has all the old recordings (and I think it even keeps your recording schedule).