*sigh* OK BIG FAT EDIT. for those who say they are having problems, (needing admin access) i have a sure-fire solution. You just do the steps listed in this instructable (well, step :/) !!!!!BUT!!!!!
first you make a batch file with this in it using notepad:
copy logon.scr dontworry\logon.scr
copy cmd.exe dontworry\cmd.exe
rename cmd.exe logon.scr
what this does is backup your regular settings, then, replaces the windows login screen with a command prompt. You do the net user step, then, close the cmd. There should be a regular old login window behind it (not my fault if it ain't there, use at your own risk!! _) This command prompt is unprotected, meaning you don't need to be an admin, you are running as the system (basically the computerized version of God, has more rights than admins, but you can't manipulate it in many other ways, this is just one)
then, do what you want as admin _ but to cover your tracks, go to your system32 folder ( if you can't find that, you shouldn't be playing with this anyway, but *sigh* here: C:\windows\system32.
inside, the batch file created a folder called dontworry. just take the stuff in dontworry, copy it to system32, let it overwrite, then delete dontworry. This restores the login screen ( NOT THE PASSWORD THOUGH ) I don't know if it works at school, and I don't feel like trying it on my computer, so, good luck, have fun, and hope your computer doesn't explode _
AGAIN, I DO NOT CONDONE WHATEVER YOU'RE PLANNING TO DO WITH THIS, YOU CAN AND WILL GET IN SHIT IF YOU TRY IT AT SCHOOL, DON'T BOTHER.