Can’t access admin panel

I am trying to fix a Word Press site that was messed up by previous web master. It was originally at 2.8.4 but had numerous errors. The wp-includes folder was missing for starters. I appeared to get all the errors corrected but could not access the Admin panel because I kept getting message an upgrade was needed. I successfully completed the upgrade to 2.9.2 and now I get to the admin login screen but it does not recognize any ID or Password I use. I requested the lost information by email and even that does not work. How can I access the admin panel?