Most, in not all HP's come with a program that will do it for you. It will even remind you every single week until you do it. It's probably on Compaq too, now. Don't know about other computers, though.
Right after Thanksgiving dinner (around 7pm) me and my agents (friends) will setup camp in all the major retailers to grab the most wanted items first. That's my plan anyway, but in reality I'll probably wake up at 7:45 on Friday, then go about 90 down the highway hoping that it's not too late.