I suggest downloading Visual Studio in either its "Express for Windows Desktop" Edition or the Community Edition. Both of these are free and they don't expire. They will let you develop programs using Visual Basic .Net.
http://www.visualstudio.com/en-us/downloads/download-visual-studio-vs.aspx
Other that that, you can try to uninstall the demo and then install it back again. This should get your trial period restarted.