It's been discussed online.
I’m pleased to announce that we’ll be providing official support for Windows XP, in addition to Windows 7, with Photoshop CS6.
We know that some of our Windows customers were concerned about Photoshop CS6 dropping Windows XP support similar to Lightroom 4.
We will, however, be dropping official support for Windows Vista (Please note: although Windows Vista is not officially supported, we do not restrict users from installing and using Photoshop CS6 on their Vista Systems)
Why is Photoshop CS6 still supporting Windows XP?
Quite simply, Photoshop’s user base is much different than Lightroom’s and many more of our customers are still on Windows XP. However, the number of our customers on XP is decreasing and we expect to see more and more of our customers to migrate to Windows 7 and Windows 8."
So Vista is not officially supported but it will run CS6. Make of that what you will.
Any reason you're still on Vista?