Ok, I am trying to print a page from a windows service that I installed using a Visual Studio setup project.
At first I set the Account property yo Local System, but it
I wouldn't recommend using interact with desktop. You will run into compatibility problems on Vista, Windows 7, and later versions of Windows.
You could use WTSQueryUserToken to get a user token for a logged on user and then print from that user's token. You could do this using CreateProcessAsUser to do the actual printing.
To get the logged on sessions you could use WTSGetActiveConsoleSessionId or WTSEnumerateSessions.