<p>When userA uploads a file, his files will be uploaded to folderA, when userB, to folderB, and so on. Roles/Profiles in ASP.NET. Folders will be pre-existing. Anyone?</p>

You'll probably want to hand-code that. There's nothing intrinsic to ASP.NET for managing user files. However, the code to do so should be relatively easy. Assuming the username is unique and never changes, you can combine the username with a path (use Path.Combine) and upload to that location. I would also lock down that location so that nobody else can access it.