>I am about to upgrade a client's application from VFP 6 to VFP 7. I am also in the process of replacing some of their computers. If the client computers are running the client install of VFP 6 will the be able to run a new VFP 7 executible or must they all be upgraded to VFP 7.
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In order to run apps compiled with VFP7, you need the VFP7 runtimes and their dependent components such as MSVCRT70

>Also if I install the client set for VFP 7 on the new computers will they be able to run a VFP 6 executible.
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VFP6 apps can execute under the VFP7 runtimes in the vast majority of cases. Both the VFP6 and VFP7 runtimes can be present on the same machine.