Speak to the person who is the administrator, and ask them to sort it out, if you are meant to have access to it, then I am sure they will be willing to change it for you.
Heh that progam is old as dirt... hehehe... i got kicked from my schools net for having that on my network files... but it was like one of the last days o school... 8th grade year... graduated in 03... yea i stuck it to the man
You can't just log into XP Administrator from safe mode without a password. That only works if no password was set originally.
Anyway, you don't know this guy's real intentions. Cain and Abel are good for some things, but they just take far too long to crack passwords. Seeing as Windows passwords are encrypted using NTLM and SYSKEY, which is near as damnit unbreakable, you'll get nowhere anyway.