What happens when you try to reinstall LW...are you getting an error??
Did you uninstall your old LW before trying to install a new version? If so, how did you uninstall LW (ie via start > all programs > LW > uninstall, or via Add/Remove Programs)?

If LW kept restarting & you didn't have 'run on system startup' ticked in LW's tools > options > advanced > system startup...it may be that you have a worm.

The thread below has a few different fixes to try, if you think your computer might be infected.
http://www.gnutellaforums.com/genera...s-options.html