The Focusrite Saffire range presently has drivers available for the 32 bit version of Windows Vista. These drivers can be downloaded at http://www.focusrite.com/downloads/
Support for Vista x64 is currently in development but is NOT yet supported. Please check back on this article from time to time to learn about updates.
* Some Vista 64 bit users have been succesful booting into 32 bit mode by holding F8 on their PCs during boot. Then they were able to install and use the Saffire.