If you are trying to install the App-V 4.5 client and it's dependencies as MSIs rather than using the EXE installer you'll probably run into issues deploying the DW20SHARED.MSI. I found on the Technet forums that this poperty needs to be specified APPGUID={4C1CE627-6B28-436E-BD12-3A881065FB20}.
For App-V 4.6 the property is APPGUID={9E9D30B2-2065-4FDE-B756-8F1A6EABAFC3}
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