Help! Newbie mistakes, wake of external hard drives in my path

Thanks in advance to the people on this forum who know what you are doing. Hopefully you can help me.

I thought external hard drives functioned like flash drives, and that you could move them back and forth between Mac and PC. I guess not.

So, I didn’t format the drives, I didn’t partition the drives, I did move them back and forth between Mac OSX and Windows XP. As you probably guessed, whenever I try to read the data on either machine, I get a “format disk” request. I have not reformatted the drives because I am hoping for a miracle that someone can help me get the data back.

External hard drives that I have messed up in this fashion include a MyBook and a Passport, as well as one from another manufacturer.

What can I do to recover this data?

P.S.  I didn’t know any better, so please go easy on me. I promise to properly format and partition my drives in the future.

Hi there, what if you try TestDisk? It’s a free data recovery software able to revoer most corrupted partitions, it’s what I would try first!

Hope it helps!