FDISK It!!
More likely than not, if the laptop has come from a school setting there are most likely policies set on the machine using poledit.
If you cancel the logon screen and it gives you an error and then the logon screen comes back,, I would say that a LOGON is ENFORCED by policy,, disabling you from circumventing this,,
Two options,,
1: F8 will get you to safe mode as already stated,,, once there,, load POLEDIT for WIN95 onto the laptop,, and yes i did say WIN95 on purpose,, once loaded ,, Open up Poledit,, go File,,connect to registry,, and then go through all the options and uncheck anything that says disable or enforce,, then OK,, then save ,, then reboot,, If you uncheck the correct ones,, you will fix it without reinstall
2. FDISK it,, and then format,, and then reinstall,,
cheers
