It is a bit confusing on the MS site. When you register the serial it will say that its out of warranty, but if it has a disclaimer about the 3RROD.
Only difficulties I've heard of is where you buy the 360 2nd hand and someone has already registered it as it wont let you register the same console again. If however you bought it from a friend you can always just get them to process the RMA.
And opening the 360 makes no difference either. They aren't even bothered if its been hacked or if the warranty sticker has been removed. They'll still fix and it and return it to you (un-hacked usually!)
Only difficulties I've heard of is where you buy the 360 2nd hand and someone has already registered it as it wont let you register the same console again. If however you bought it from a friend you can always just get them to process the RMA.
And opening the 360 makes no difference either. They aren't even bothered if its been hacked or if the warranty sticker has been removed. They'll still fix and it and return it to you (un-hacked usually!)