Depends on what Operating System. I'll assume XP?
If it is truly the administrator account (check by starting in safe mode and choosing administrator).
You can do a repair install (install on top of itself without deleting the existing install), then during the first reboot while it tries to load drivers, hit CTRL-ALT-DEL, clcik file, open, type CMD, change the directory to c:\windows, type "Net User Administrator *" and it will let you change the password (if you just type "Net User" it will list the users
Astrophel, February 2009
