There is no way to delete the local administrator account, so don't
worry about that. Maybe you renamed it. Do you have any accounts you
can login to this computer with? If so, go to start, run, type cmd
and hit enter. In the window type "net user" (without the quotes) and
hit enter. This should bring up a list of your local account names.
Try to use the account that you might have changed your administrator
account to. If you see and "Administrator" account, but the old
password doesn't work, you may have to reset the password. Here's a
good utility:
http://home.eunet.no/~pnordahl/ntpasswd/
Good luck!