Hey man, i gots da same problem at my school......
but MS-DOS wont allow u to change the password purely because u dont have admin rights.
y wouldnt u want the admin password anyway?! u could do so much more!
gettin the admin password is pretty easy......just download ubuntu ur someother linux based OS, then boot ur system off that.....along the process, the new system will give u the admin. password.
u can log on as an admin......but as far as accessing network drives, ur school's IT team may have assigned a password to them, so that u may not access them without yet another password......