I've searched all over for an answer and cannot find one. I have a DS Lite with Mario Kart. When I went online for the first time, it said something about my copy of MK being tied to my DS. Now my son has some birthday money and wants to buy his own DS. That's great, b/c we can play against each other w/o buying a 2nd MK cartridge. However, what if he wants to borrow my MK cartridge and play it on his DS? If it is "tied" to my DS, what happens when he goes online (or tried to go online)? Has anyone had first-hand experience with this? I cannot find anything in the manual or any online FAQs and a Google seach has (thus far) turned up nothing.