For those who recently upgraded their PC video cards to support DX10, you’ll be happy to know that both Episode Two and Team Fortress 2 will support the advanced technology of these cards, even if the PC is running Windows XP. On the low-end front, Valve still plans on supporting PCs that can only run DX8 applications. Valve’s attempting to also support DX7, but couldn’t confirm if it’d go back that far with technology.
Intriguing. It will support DX10 features on Windows XP which doesn’t have DX10 available? I am wondering if Vista will offer any additional features to the game over XP though. Hopefully not…
Source: Game Informer