I have been using Firefox for years. It is a good browser. It is faster than Explorer, which was a bigger issue when I still had dial-up than it is now. I also use PC Tools Spyware, available from Google free, to periodically scan for adware. It will scan your machine, then clean it of infections. Since I don’t open emails from people I don’t know, I haven’t had a problem with viruses, as I understand that that is the way those things are spread.
If you use Firefox, James is right, you don’t need to eliminate Explorer. Just don’t use it. I must use it periodically, as not all the web sites I use are compatible with Firefox. So I use Explorer on those sites, then close it. This computer is online about sixteen hours a day, for two years and I have had no viruses. Plenty of adware, which the PC Tools Spyware eliminates.