the file system is currupted , few things you can do
1) use data recovery software i recommend these: easy recovery pro/file scavenger/r-studio/getdataback/finalrecovery , of course non of em is free..
2) cant say for sure it will work as i never had expirence with it in such a data loss situation , ive heard linux can read currupted file systems better , use kanotix or knoppix (linux live cds)
http://kanotix.com/index.php?&newlang=eng http://www.knopper.net/knoppix/index-en.html
and burn the data to cd/dvd or copy it to your other hd (linux have pretty crappy ntfs write support,so if your wd 20gb isnt set as fat32 forget about that idea or use acronis disk director suite 10/partition magic to convert it to fat32 without data loss)
3) take your chances with chkdsk (might make the situation even worse,but might also restore the partition to a readable state)
goto start-->run-->cmd and put this and press enter
chkdsk /F /R X:\ (replace X with the partition drive letter)
if your gonna do #1 or #2 , after done just format that partition so it will be usable again , and no matter which one of em your gonna do after its all done better use powermax (maxtors diagnostic software) to get it checked
also i wonder , did you overclock before it happened? some mobos currupt the hd when the overclock is too high for em to handle