Alas, even Google doesn't know what an "odd lettered file" is. Your post is the only hit, and you don't explain it. Maybe the error message stated something else then you write.
Anyway, if you don't have a backup (an 'image') you lost everything on the c:-drive. That means that it's time to find out if ctrl-F11 to restore it to factory conditions still works. If not, Dell might be able to sell you the recovery disks.
I was in the process of compressing my C drive on my Dell Inspiron laptop. About 25% through I received the black screen stating a odd lettered file is compressed and to use ctrl-alt-del to restart. It won't restart and just loops. Any ideas ? I do not have the original disk.