When upgrading to Vista SP2 from XP, you may get an Application Compatibility Warning for the Microsoft Application Virtualization Client
When you upgrade from Windows XP to Vista with the Application Virtualization client installed you may see the following report:
Potential issues were detected with installed applications/devices
These issues do not prevent your upgrade, but some applications and/or devices might not work once your upgrade completes.
* Microsoft Application Virtualization
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB960782.