The contest is part of AMD's recent plunge into social networking and will be a twitter based contest. The way this works is that you have to follow @AMD_Unprocessed on twitter. Every other Monday starting on the 27th of July @AMD_Unprocessed will tweet an AMD related question. You should answer Via Direct Message these correct answers will be put into a drawing for one of the four Dv2s. This cycle will repeat for the next two months.
Not too terribly hard to enter, or course you never know what question they will ask, but I am sure that whatever it is can be found quickly by checking out AMD's website unless I am completely missing the mark.
The downside to this is that it is only open in the US and Canada to people over 18.

Full rules and details can be found at www.amd.com/40years.