>>I see. It will be the same also if I try to copy my file to ProgramData folder using WE, right?
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>Yes.
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>
>>
>>I plan to test your original FSO.DeleteFile right now, but in the meantime I delegated the problem to the people who create installers as I don't think we need to change our application code to fix the issue - there may be too many places where the code will need to be fixed.
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>:o)

I've uninstalled our software and re-installed and everything seems to be working.