singingchix,
Yes, you can install FF without touching IE. Same for the other browsers. I keep IE loaded b/c there is one site which I frequent which is only about 95% compatible with FF, so I have to use IE every once in a while for the 5% which isn't compatible. I actually use a beta FF, in addition to the regular one, IE and Chrome -- all installed without issues. You can go into your default programs under the "Start" ("set program access and defaults") menu, and set your default browser to whichever you want.