If wols' solution doesn't work...
I've had this occasionally in Win2k Pro, but could always get to the task manager, kill and restart Litestep, run explorer, etc.
Does ctrl+alt+F1 work? If Litestep is running, it should. Also, try ctrl-alt-del twice instead of once...I don't know if it does the same as Pro, but try it...you can run stuff from the real (NT/2k) task manager.
If the ctrl-alt-F1 menu comes up, go to run, and you have two basic options for getting things back:
1. Run regedit, then search the registry for litestep.exe. Hhen you hit an entry called "shell" under one of the xxx\Software\Microsoft\whatevers, that should be the one. Change it to explorer.exe (no path should be needed) and restart.
2. Run explorer, then in the listep\themes folder, open the file "themeselect.rc" with a text editor, and make it like this: