It’s not uncommon that with time Windows may take way too much time to start up. One of the reasons for bad startup performance are the applications that are launched during boot up.
UAC (User Account Control) is an extra layer of security introduced in Windows Vista. It suspends any application you want to run: a dialog box pops up asking for an explicit permission to run the app. While offering extra security, UAC certainly complicates remote support because you lose control over the remote machine in some cases.
But let's see what other options we have here. All workarounds suggested are for Windows 7 but they also should work in Vista and Windows 8.