What is the fastest internal hard drive I can get for $100-$200 or will I need to spend $300 to get a really quick hard drive?
In that price range this 150gb Velociraptor is the fastest thing you can get. http://www.newegg.com/Product/Product.aspx?Item=N82E16822136296
150gb is not very big but it would work great for Windows and programs just have a different storage drive.
The 300gb version is $229 http://www.newegg.com/Product/Product.aspx?Item=N82E16822136322
If you want a larger drive then as 505090 says the WD Cavier Black series is my favorite. The Seagate Barracuda 7200.12 series and Samsung Spinpoint F3 are also good. The larger of the drives are the fastest due to higher platter density.