damaged archives on NTFS disk after chkdsk run

Hi,
I've got an external 100GB USB disk (NTFS) that I've sometimes
disconnected without unmounting. It has been set up for fast removal,
however. When I wanted to defragment that drive I was asked to run
chkdsk first.

Chkdsk found a couple of bad entries which landed in folders like
"found000" and "dir001.chk". Nothing I'd really miss, so I deleted
most of that stuff. Some folders, however, could not be deleted,
"access denied".

So I ran chkdsk again but nothing changed. Then I defragmented that
drive.

I have a lot of rar archives on that drive which seem to be all
damaged now. Extracting these archives results in CRC-error messages
and 10 - 30 % of the files missing. Can I do anything about it?

Any ideas on how to recover my files?

Best regards,
Dieter