Lost Usernames on XP machines

I recently came into the club and I have to install certain software onto four XP machines. The problem is they use the same password for all of them but can only remember the username for 2 of them. They have limited accounts for all the machines but its the administrator accounts I need.

Is there anyway I can locate the usernames so I can reset them and work away. As was mentioned I have the passwords just not the username.

Any and all help on this would be greatly appreciated.

Thank you

BW