I wrote myself a little downloading application so that I could easily grab a set of files from my server and put them all onto a new pc with a clean install of Windows, wi
Directory.CreateDirectory() should do it. http://msdn.microsoft.com/en-us/library/system.io.directory.createdirectory(VS.71).aspx
Also, in Vista, you probably cannot write into C: directly unless you run it as an admin, so you might just want to bypass that and create the dir you want in a sub-dir of C: (which i'd say is a good practice to be followed anyways. -- its unbelievable how many people just dump crap onto C:
Hope that helps.