Find a friend who will grant you shell access to their home system running on port 23.  Or set your own to run on port 23.

EDIT: Oops, didn't notice you said telnet was disabled.

Oi, that is one thing I hate... libraries which feel compelled to nail their computers down like that... some people.... ick

Try bringing an old DOS boot disk and putting that in the drive and resetting, but that's a pretty long drawn out solution which may or may not work