Well, the way I read the reply here, is that you don't believe what I'm typing..
Hopefully that's not the case, and your just stunned that M$ is using a Service Host process to "Own" and deny access to files while UAC is enabled.
If your issue is the prior rather than the latter, GO GOGGLE
"trustedinstaller owns program files"
Edit: I had a power point listed here, but I'm looking for a better example..
Gabriel Dungan
Edit: This explains somewhat the trusted installer..
http://groups.google.com/group/micro...82e0e?lnk=raot