>>Each encryption tool has its good and bad points, and each can be defeated if the user wants to bad enough. The best one IMO is konXIse - http://www.xitech-europe.co.uk/ - which is what I use. You can only use it on VFP EXEs. APP files are not supported. konXIse also compresses the EXE as it encrypts. When the EXE is launched, it is "expanded" into RAM, so a hacker could use a utility to write the memory to an unencrypted file, then use Refox to decompile it.
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>Do you know if I can use KonXIse with a COM EXE? I wrote to the Xitech people but got no answer.

I am not 100% sure, but I see no reason to prevent you from doing that. I'll compile a little demo COM EXE tomorrow [Friday], encrypt it with konXIse and try to run it.