I used VS2010, and target for .Net 2.0 (VB.Net Windows Form application)
How to decide what is the .Net target I decided on 2.0 because I understood it will be OK if
You should build an installer (a Setup/Deployment project in Visual Studio) that includes the 2.0 redistributable so that when your clients install your software it will install the necessary .net framework for it to run.