Lost categories

Last night I upgraded to 2.6 from 2.0.1. Everything works fine except for have lost all the categories. There must be a file that I deleted that contained the category listing. I would thing that it would be in the wp-content folder but I don’t see anything there. The old site is completely backed up so I have access to any file that I need. Anybody know how to get the category list back?
Thanx