I am using windows 7 with visual studio 2017. I have some code I want to run on windows CE 4.1. How do I build the code for this version of CE? I see there is mention of a CE build platform 4.0 but can't find a download for it?
It depends on what kind of application do you have. If has been developed with Visual Studio probably you should be able to build it in an old version. VS2008 or VS2005 should still support CE 4. For sure they support CE 5,6 and 7. It may be that the application has been developed with Embedded Visual C++ 4.0, you may be able to still find a download in MSDN but I've no idea about how it could run on Windows 10, maybe a WinXP virtual machine would be better. If the application was developed using platform builder and integrated in the OS image you can still find it in MSDN but, again, this is quite an old tool and will probably have issues running on a recent PC.