As Celestial Heavens wrote in September, one option to win the desired PC is to participate in the Dark Messiah Machinima contest – the requirements are to finish a comic story and the best entry will be the winner.
You can also join Dark Messiah official fansite Disciples of Sareth, complete a series of missions and earn most gold among all to win the PC. However, comparing with the Machinima contest, Disciples of Sareth offers other prizes as well, including 5 iPods, 10 Ubisoft gift cards worth 100$ each, lots of Dark Messiah and Heroes V T-shirts, mousepads and stuff like that.
Just recently Ubisoft announced the third (final?) option to win the PC by participating in "Gear up to win" Sweepstakes. Similarly to Disciples of Sareth, in addition to the main prize it is possible to win lots of other prizes as well, including 2 Logitech customized speakers, 15 powerful NVIDIA Geforce 7950 GX2 graphic cards and more. You can read the full rules here, and please also note the age limit. The only real requirement – you’ll need something like Nature’s Luck to win!
The Disciples of Sareth prizes can be sent out only to US and