Quote Originally Posted by riehlman
... I can save new files but I cannot retrieve any old files.
Doing this greatly lowers your chance of any recovery, as the new files may well overwrite the old.

This really isn't a Knoppix or Linux question. Unless this was a very deliberate virus attack, the files were likely somehow deleted but a normal delete only removes the file table entries, not the file data itself. As most USB flash drives are partitioned as FAT drives, you should be able to use any number of programs that examine a FAT partition and try to recover deleted files. I would suggest a Google search, Google is your friend (A.K.A. S.T.F.W.) Writing additional files to the drive likely overwrote some of the data sectors of your old files, so you likely will not be able to reciver everything, but if only a small test file was written you may be able to get back all but one file.

This post will be moved to lounge forum, as it's really not about Linux and hardware issues.

Quote Originally Posted by riehlman
Help.
Do you really think that adding this to the post increases your chance that someone will try to assist you?
Or to ask it another way, do you think that if someone read this without the "Help." at the end they would have just decided to pass it by, but with the extra command to help you they would respond?