Also take a look at this site, it's IDE is much smaller and faster than the hughely swollen MS Express C# deal.
SharDevelop is a free IDE for C#, VB.NET and Boo projects on Microsoft's .NET platform. It is open-source, and you can download both sourcecode and executables from this site. http://www.icsharpcode.net/OpenSource/SD/
See if you have something like "C:\Windows\Microsoft.NET\Framework\ ..." on your computer. That may be all you need.
Also, let me warn you, C# will make your fingers sore with all the typing you will do!