But that's why we made the Sideload Wonder Machine
Oh, by the way. In case you were hoping AT&T had changed its ways when it comes to locking its phones into the Android Market -- not so much. There should be an option in the picture above on the HTC Inspire 4G that says "Unknown sources - allow installation of non-Market applications." But, obviously, there's not.
That's not to say there aren't ways around it. The Android Sideload Wonder Machine was designed for phones like the Inspire 4G. So don't forget who's got your back. (Hint: It's us.)