Could give away the product-code though, so who of ~FUN~ doesn’t have Half-Life 2 ?

Yeah, who dares not to have it?

Tim Sweeney: The Gears of War experience on Xbox 360 taught us to optimize for multi-core, and to improve the low-level performance of the key engine systems. This has carried over very well to PC. The division of UE3’s rendering and gameplay into separate threads, implemented originally for 360, has brought even more significant gains on PC where there is a more heavyweight hardware abstraction layer in DirectX, hence more CPU time spent in rendering relative to gameplay.
Also, the 360 work we did resulted in an engine that also runs well on low-end and mid-range PCs. This is very important for games today; the high-end PC gaming market alone is not big enough to support next-generation games with budgets in the $10-20M range. You need to run on ordinary mass-market PCs as well. In reading PC gaming websites, one might get the impression that everyone owns a dual-core PC with a pair of $600 GPUs in SLI configuration, but the reality is very different. More than 80% of PCs sold today are still single-core, and have very low-end DirectX9 graphics capabilities. Unreal Engine 3 supports those configurations well.

Some XP vs Vista gaming info:
XP vs. Vista - A Tale of Framerates