Hi
I always delete or change files on my Hard Drive 'C:' when LimeWire isn't running. I find this the most effective way.
The files you are sharing are stored by default in:-
C:\Program Files\LimeWire\Shared
This is where all your files are downloaded to. The library is just a reflection of what is in 'Shared'. They are not on LimeWire!
So don't delete any songs from your 'Library' that you just want out of there, because you will delete them completely off your system.
Does that make sense
Good Luck