if your on xp this shouldn't be a problem at all.
open taskmgr (Ctrl-alt-del) check the proccess tab if litestep is still running end process or end process tree(i prefer end process tree).goto File, new task... run LS.

if this fails to bring LS up goto file, new task... again run explorer goto the to LS dir run the "switch to default theme.ink" or in the utilities dir setshell.exe

hope this helps