What about tackling it from a different direction entirely. I'm not sure if everyone's familliar with the BNETD project, but what they did was build their own program that emulated Blizzard's Battle.net servers. So clients could connect to them without any kind of system/software checks. I'm sure Live! is pretty complex and that it would take alot of work, but I think it would be alot more feasable/sucessfull than trying to hack MS' Live! Like yasman said, because you have to connect to their server they have a ton of ways to detect and block you.