The VB6 version runs on any Windows NT, 2000, 2003, XP and of course younger versions.

The .Net version needs the .Net frame work, a completely new way for Windows to talk to the processor. While it has certainly aesthetic and design improvements over the old ActiveX architecture, the sad truth is that .Net is very processor power hungry. I would recommend a Vista or Windows 7 machine because those versions of Windows have the >net framework natively built in. For production I recommend a powerful 64 bit machine with multiple processors and 8 gig ++ of memory.