I've just been having a look on my CDs, but I don't seem to have saved any Firefox setup files. Incredibily, although they have previous versions of Internet Explorer, Opera, AOL etc. oldversion.com do not have any old versions of any of the Mozilla browsers.
I'm going to my sister's shortly, so I'll take my USB pern drive and see if she has the Firefox setup file on her system. If she has it, I'll copy it and if you want it I'll send it to you via email.