Randomly my internet slows down to a state where it is unusable. The weird thing is most of the time my internet runs fast. Why does it randomly turn slow and then turn fast? Is there anyway to fix this?

another computer in your house using all the bandwidth??
Torrents running??
Got any lame apps like 4oD that auto downloads things?

Try and eliminate possible problems.

For example, try booting your computer in "Safe Mode With Networking", then use IE with deafult settings (Just to eliminate possible problems with extensions and etc, that would be on FF or Opera). If it still continues to do that, then try hooking up another device to the router. If it has slowdowns to then there is something wrong with the router/internet connection. If it doesnt, then there is a problem (most likely) with your network hardware on your computer (Your ethernet port most likely).

There is another computer, but I use a router and my USB connector is very close to the router. I have Firefox which asks me before I download stuff. What are torrents? I don't have any add-ons on firefox.