My school uses Fortress. Google it if you don't know what this is. Me, being an adventurous person, decided to play around. To completely bypass the system, just hit CNTRL + ESC. (This was tested on Win 9x only, may work for nt/me/2k/xp, not sure)

This will come up with the password input screen. I don't think I'm allowed to elaborate.

*Most school computers DO allow access to the A:\ drive. So does fortress. Thats just a little...erm...hint.