I haven't tried it on a compressed drive - but when my 5 yearold HDD failed (OS mostly) the Slave wheeze (with jumpers set correctly) did the job. But compressed drives? Fine if the headers (keys or whatever) are not corrupt. I have used Norton Disk Doctor but not on compressed drives. It saved one file.

Now ask yerself - FAT16 Fat32 (or unlikely NTFS) - you need to know.
reloading the OS on a new HDD - don't try anything that wouldn't have been there before - if you can remember or figure it out.

And if timely lessons are in order what happened to those regular back-ups? I use 2 HDD and a removable now. and DVD re-writers are so cheap if your set-up can take one.