Foolishly, I moved a mac formatted drive into a PC... opened Disk Management, and tried to populate the drive. The drive now appears to be unreadable on either a mac or a PC. I didn't do any reformatting (just clicked the "populate" button).

I think it's just as simple as needing to tell the drive that it's still formatted for HFS/mac.... however, I don't know how to go about doing that.

Will I be able to use MacDrive to recognize the in-limbo disk? Or will I need to go a different route?

Any help is much appreciated of course.
Thanks.

Try TestDisk (freeware):
http://www.cgsecurity.org/wiki/TestDisk

Thank you very much!
It definitely recognized the drive and I'm able to use it to create a back-up image it looks like. Much appreciated!