weirs problem with my back up HD

I recently put a new 40G Maxtor HD in my comp and when I did this I still had my old HD connected. During the installation of the a new OS I had some serious problems. I believe I didn't have my "pins" in the correct positions; so my old HD has partitioned itself down to 10MB (from 20G). I've tried using partition magic with no luck. I know that my computer reads my old HD as having a MBR (Master boot record) file on it. My real problem is that I have some important info on the old HD and I need it so I haven't reformatted. I've tired using the Win XP recovery console, but when I tried to "fix MBR" it said I might lose my info. I wanted to know if anyone has any other suggestions before going ahead with "fix MBR".