Reset admin password

In windows XP OS, the admin will be given the at most permissions next to that of system. So if you want to reset your admin password from an limited user account, then try to get system level access either by scheduling the command prompt "cmd.exe" or just by cracking the "SAM" file in your system.
To schedule the command prompt
open Run -> enter cd.. (goto root)
C:>AT 7:10 interactive "cmd.exe"

at the given time a new command prompt with system level of access permission will be opened from there it is possible to change the password of any of the available user.

The second option is not recommended for no voice users, kindly format your system and reinstall all necessary applications, this will be my professional advice.