According to Tom's Hardware, Microsoft's is encountering a number of problems with games and their newest operating system: Vista.
Redmond (WA) - In a conversation with TG Daily, Microsoft defended itself against claims that Windows Vista does not run 90% of the games on the market today. However, while largely dismissing on one of big negative headlines flanking the launch of the new operating system, Microsoft conceded that the game rating process isn't perfect and there's at least one fix in the works.
If you weren't waiting for SP1 before, now you have another reason to.
Source: TG Daily