Starting a Interactive Process in Vista using TService

[Dezipaitor]

You do not need LsaLogonUser at all.

You already use WTSQueryUserToken which gives you a token, that can be used for CreateProcessAsUser.
That token leads to a process that is started in the logonsession of the user.
Parameter lpStartupInfo (member lpDesktop) you can provide a windowsstation and desktop where the new application is put ("winsta0\default").
That should work.