ok in school last year our class would fool around with net send. . .but our computer teacher disabled it this year and I have been trying to re enable it but I always get something like error 5 'no permission' or something like that. . . the PCS are on XP By the way/ / /  
ok so I already tried some programs, going to services (they both get error 5) and I even tried booting into safe mode but even when I boot into safe mode the PC still boots into the user log-in scree ( the type where you have to type the user name and password, since wee are a WHOLE school and ~300 per grade)
I already tried login in as administrator with no pass but it won't let me. .

so if this is possible please help