1. Control-alt-del & open process manager & force LW to quit.
2. Deleting your LW Preferences folder; instructions here:
Point #3 in Fixes for Limewire (sample image included at bottom of page.)
3. Reboot
Then try installing again.
4. If still problems you may have a virus that puts an item into your startup folder. Visit & register here
NorbiesWorld (click on link)