Hi Günter The Microsoft Upgrade Wizard should start when you open a VB6 project in Visual Studio 2008 or 2010. It will convert your app to .net - hopefully should be fairly self-explanatory to use. You often get lots of errors and warnings generated when you use it but usually are pretty quick to sort out.
It looks like there are issues with using .net framework 4 with ArcDesktop, so you'll probably have to develop with 3.5 instead. You can use Visual Studo 2010 or 2008 as they can both be used to developer with .net 3.5. Personally I'd use 2010 because it's newer (and better?).
yes, I guess I'll stick to Visual Studio 2010, using framework 3.5. Thank you for your hints. Meanwhile I have searched the MS help a little more in detail and in fact it only confirms what you are saying. Looking forward to a lot of work .....