This is a great site for Firefox users.
Firefox Help, Tips and Tricks
I'll have to give the follow from that site a try-
Firefox is slow to load initially on Windows XP. You can speed this up a bit by using XP's built in prefetcher. Simply right-click on the Firefox icon you use to start the browser. Add the text /Prefetch:1 to the end of the line in the target field.
The whole line should look something like the following:
"C:\Program Files\Mozilla Firefox\firefox.exe" /Prefetch:1