You could probably get a decent universal remote for this projector and do things that way. I'm not sure of the control or anything else with this projector, but what exactly are you looking to do?
I personally would find the IR codes at some place like http://www.remotecentral.com
and get a remote that works with the display and go from there.
USB control or serial control on a projector that is 7+ years old in design is not something I would place a lot of faith in really.
Hope you didn't pay more than 100 bucks or so for it.
- Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.