Firefox is my primary browser, but I also have Google Chrome.
I have never used Explorer.
There is no problem having Chrome as a secondary browser...Try it.
Make sure that you have the latest Firefox updates, or just reload it.
Not a tech, but...
I am running the same setup you are XP (sp3) on an old Dell 4550, cable modem, and Firefox.
I have had very few problems with Firefox. The ones I did have were:
* A compatibility issue with some AVG plug-ins
* A compatibility issue with Google Chrome when I tried installing Chrome.
My Explorer doesnt work (tried updates, reloading, etc - nothing. But that’s okay b/c I prefer Firefox anyway.
I don’t think your problem is with the browser, necessarily.