TESTDISK is a DOS-based FREE utility that you can use to recover deleted/damaged files/partitions but it can be difficult if you don't have any idea about what you are doing.
When you're recovering lost files/partitions, it is not as simple as it sounds, you get a lot of "ghost" files/partitions, that were on the drive before. The idea is to not use destructive recovery methods right away (writing on the disk that you want to recover data from), use the "preview" mode and recover data by copying file by file to another HDD before attempting to do any actual partition recovering.
The only commercial utility that I used successfully is GetDataBack and I used quite a few when my Samsung drives decided to "drop" some partitions out of the blue. They were F1's and T166S's. Coincidence? Maybe. But I decided to stay away from Samsung drives and ATI's SB600-7x0 that week. Unfortunately it is a commercial software.
I just found out about this software: PC Inspector File Recovery 4 that some sites out there report good things about. Check it out, it is free apparently.
@ctive partition recovery software for me behaved strangely. It seemed to work, and it did with smaller files (<1G

but with large files (>1G

it only recovered the first 1GB of information, even if the file seemed to be OK. I had a few HD rips that were big files, and the movies were incomplete at playback. Just a warning. Maybe it will work for you, test it first.