Not gonna happen.
The tower isn't the whole part of the setup. That's why it was called an "Alpha Xenon Kit". The G5 was acting as a drop-in replacement for the early Xbox 360 development targets. It booted into a customized operating system that would then wait for commands from an external computer running the development tools and remote debugger. Without the other half of the setup, the software on the G5 was quite literally useless. The system I saw running didn't even have the Xbox Dashboard installed- they were *that* early. It had a launcher menu that let you load executables directly, and that was it.
From what I've been told, getting the software for these machines (even if you have authorization from Microsoft) is becoming extremely difficult. I don't think they're giving it out anymore unless you already had access to it, which means you would have had to have been developing for the 360 as early as 2004. Likewise, even if you did get access to the SDK, and the Xenon OS that ran on the G5, you'd hardly be able to do anything with it- code written for that setup isn't going to run directly on the 360 and visa versa (not that there's a plethora of 360 SDK examples floating around to begin with).
So, unfortunately, you've basically got a bog standard G5 there with a few fancy Microsoft stickers on it. Unless you have some REALLY good friends located fairly high up in a major game development studio, you're never going to get the software for it. It's never been dumped and released publicly, anyone with the resources to do so has generally been more interested in working with the later 360 development units (the ones with the sidecar that has the low level debugging FPGA and extra RAM installed in it). These systems have pretty much been forsaken and forgotten about.
-SC
