What version of XP ? Did you give the admin acount a password ?
XP Pro
1)Remember your password or if you left it blank, leave it blank again
2)Login with the acount Administrator by pressing CTRL-ALT-DEL twice at the login screen
3)Make the other account a regular user and remove the password
Xp Home
1)Restart in safe mode
2)Login with administrator account
3)Make the other account a regular user and remove the password