Help needed>> File recovery method or software

We're in need of direction to recover files from an external USB drive (250G). Only one directory remains from a huge tree. The drive has been our storage and/or backup drive for last few months as family members transition to newer equipment and clean up hundreds for files.

Unfortunately one user pulled the USB plug from their computer while computer was being scanned by an anti-virus application. (At least that's what we think has happened.) Drive comes on and a single directory is shown which is only one of what was once a multi-tiered directory. Nothing else shows on the drive anymore.

I've never attempted to recover files and directory from a drive and am hoping there is some software out there which could help us. We've got some compiled photo albums, family history, etc which were just transferred to drive day of the error for a drive backup task.

Is recovery even possible??

We are using WinXP Pro on a server and most of the systems in use (4 laptops, 3 desktops.) A couple use WinXP Home. External USB drive runs USB 2.0 and is a WD 250G.

Any ideas, recommendations, or comments are welcome. We're relative newbies and need some expertise as the quoted $300 by a drive recovery service to get our files back isn't available.

Thanks in advance.

P.S. - Love these CNET forums. I spend 9-10hr/week minimum reading and learning from all those who contribute. What an education!!!!