yes, xp home is good for gaming as most games just require XP so either home or pro doesn't matter. xp pro is better suited for business and professionals. the remote desktop is a major gain for pro. they both have restore function.
you should be able to hook up the 7800 to the tv provided that the tv has the appropriate connections but LCD screens are portable as long as you **** puncture it or drop it so yes, they are "protected" to some extent if you care for it while carrying it and during transport.
for sli, NO you cannot mix and match the gpus. it has to be from the same vendor and the same model e.g. 6800GT. if you want a 7800 sli rig, you can only get two 7800, you cannot add a 7800 and a 6800 ultra.
your email is not enabled so i posted this.
Cameras that make great holiday gifts
Let them start the new year with a step up in photo and video quality from a phone.