It's always best to uninstall limewire via Start > All programs > Limewire/Uninstaller.....Uninstalling via the Add/Remove will cause problems.
It sounds like limewire could still be running, hence you not being able to delete the left over files manually. Try checking within your task manager (Ctrl-Alt-Del), if it is still running select the End Process option.
If Limewire was popping up all the time (the problem your Dad was having) try this fix....
http://www.gnutellaforums.com/231269-post141.html