>>>Indeed this was the first thing that I checked, but both files are in syswow64. Also the library itself does not give an error, the unzip process itself returns .F.
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>You're right, dependency usually produced a compatibility error... even so, can I recommend you put all 3 files msvcp71.dll, msvcr70.dll and msvcr71.dll in the app folder with the VFPcompression.fll and try again? If still broken, obviously you have no choice, but thr prospect of a breakage for unknown cause is alarming for others who presumably also may face this in future...
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>Only other suggestion would be that West Wind libraries include zip/unzip using standard winzip dlls.

I was not aware that msvcr70.dll would also be required, usually I include only the other two files. You are right, I should include them in the program folder as well.
However this particular client had some specific issues that were difficult to trace. For instance, right after installation, the program would work well. Then after restarting the program, it would fail. Also with elevated admin it would fail after retry, but each time after installtion it would work. So they would install the program in the morning and don't close it all day, this was the only way they could work. So far the only place that caused issues was the unzip code, but this is not certain, because it starts right at teh beginning and then the program would not proceed. So it's difficult to say which other parts would fail.

Now the VFPCompression code is in a try/catch, but the try was successful, however with return .F. therefore I conclude that it has nothing to do with the missing c libraries, otherwise it would have gone into the Catch and would show a different message. So it was more likely an error to extract the files to a particular location, however this location had all necessary rights and the code right before was also able to delete all contents in this path.

Some users worked remotely via VPN and did not have this issue at all. Aparently now it started working again in the office as well without any explanation, According to IT no rights were changed, but it could have been the difference how the installation was executed. I got the feeling that during some changes for home office, things were changed on the server that they have not told us about, or were not aware of.