I'm not sure what you mean by "installing into it's own library"...LW should install to C:\Program Files\LimeWire\

Anyway, try this: Uninstall LW via start > all programs > limewire > use the uninstall option (don't uninstall via add/remove programs). Now use your computer's search to look for all files & folders with limewire in the name. Delete what you find. If you've ever changed LW's location for saving files (downloads) then make sure that you haven't put the saved folder within program files!! Otherwise, you'll lose your downloads.

Reinstall LW & make sure to use the offline installer. When you click to download LW, cancel the dialog box which pops up. Then use the option to download the offline installer.