Looking at the data I've got, it would appear that some Xboxes use the standard "Media Center Edition" remotes that are also used on Windows PCs, and I've got those already under the "Microsoft" keysets. However, other config files are doing something completely different...

Ok, if I'm reading this right, the Xbox 360s are using the MCE remote keysets, and it's the original Xboxes that are using a different protocol. So, I've probably got your Xbox covered already. But I'll see about getting the older keyset in as well.