I remember reports of people successfully doing that a while back but I was actually reading about it in an article about Microsoft cracking down on console/user regional mismatches.
Of course after reading the article I gave it a go, created a new Live user account where the address was a US one and it did bring up all the overseas content but that was prolly about a year ago now so not sure what they've done to combat it, if anything..............tez
Bookmarks