Not sure. I installed .NET 2.0 and it wasn't there either, so I bumped up to 3.0 and it's still not there. I can't imagine that I'm the only one experiencing this problem, but I cannot determine what, if anything, I have not referenced correctly.
When I try to add a reference to my project, System.Net is not even listed on the .NET tab (it goes from System.Messaging.Dll to System.Runtime.Remoting), nor is it on the COM tab (it goes from System.Drawing.dll to System.Windows.Forms.dll). I've even gone so far as to try to find it w/ an Import statement but no luck there either.
GG, this is frustrating!