Program Compatibility Assistant Service
Windows Vista Service Details
Compatibility with old windows software, I am guessing? I havn't seen any compatibility issues yet, and I have run several DOS,win95, and XP apps.
Provides support for the Program Compatibility Assistant. If this service is stopped, the Program Compatibility Assistant will not function properly. If this service is disabled, any services that depend on it will fail to start.
Consequences of Stopping:
All services listed in 'Required For' will be unable to function