With each version of Windows, you can make some assumptions on what .NET Framework version is installed. Sometimes you need to know it on a computer that’s not yours, or you need a user to tell you what version they have, it would be very convenient to tell them to visit a site and tell you what version they have. Microsoft has a KB on this but it involves mucking around in the Windows Registry, which most users aren’t comfortable with it.
Maybe the only way to really do this is through ActiveX if it’s going to be on a website. A simple download .exe would be much easier. There’s already code for this but I haven’t seen a wide use yet. Has anyone done this on a website before?