>1 - how to prevent double click on the windows desktop ?
>2 - how to prevent right click on the task bar ?

Both require coding using a language other than VFP; there's no simple solution to either within VFP. VFP doesn't control either the task bar or the desktop as native parts of VFP, and the API calls associated with them are not conveniently accessed from VFP. I'd suggest doing some reading on Shell Extensions in the MSDN documentation for guidelines on approaches using C++ or one of the .Net languages.