This seems a strange question!!! Limewire is about sharing your"library and stuff" and if you do not wish to share then do not use Limewire.

You may mean that you wish to stop your boss/spouse/kids/teachers/dog or budgie seeing these things in which case I think you need to configure your computer accordingly. I shy away from doing such things myself as once you lose your password you tend to be in deep sxxt

In short you would have to set up your computer for different users who would each have to have separate configurations for everything. ....AFAIK if some one knows different I shall be happily corrected.