I keep getting spyware threats saying a high risk highjacker is trying to change my start page on internet explorer. I haven't been using IE I've been using Firefox so why am I getting these spyware warnings?

It is not because you do not use IE that some malware would not try to attack it anyway.

There have been independent studies that have shown that Giant AntiSpyware is the best product currently on the market today for spyware removal. You may download a free trial of it by clicking on the link below and going to the Products page and clicking on Free Downloads.

A good alternative is "Spybot, Search and Destroy". Evenly good, and free.
In combination with "AdAware" (from Lavasoft, also free) unbeatable.