After 11 long years, Adobe has decided to drop support for Windows XP in its next Photoshop update. Photoshop CS6 (13.0) will be the last major version of Photoshop to support Windows XP” said Adobe Product Manager Tom Hogarty in a blog post.
The reason for this move is due to the improved modern software features that rely on modern graphics drivers that are not available on Windows XP. They also note that Photoshop CS6 is not supported on Windows Vista. The advanced announcement is to allow companies that still utilize XP ample prep time to shift to newer operating systems when the time comes.
Source: Photoshop.com Blog