The Master Collection and Cloud service list Windows 7 and XP.
XP can not be supported since it is 32 bit. Must be a reading error on your side.
Thanks for being rude and snarky as always Harm but it might be wise not to be so lazy and check the tech specs. Some of the 64 bit programs will not workwith XP but there is still XP support and no Vista support. I find that odd. I don't think it is a reading error on my part but in fact your love for being rude and snarky when ever possible : )
From your own link:
Microsoft® Windows® XP* with Service Pack 3 or Windows 7 with Service Pack 1; Windows 7 with Service Pack 1 (64 bit) required for Adobe Premiere Pro, After Effects and Encore; Windows 7 with Service Pack 1 required for SpeedGrade
PR, AE, and EN require Win7-64, SG requires Win7 and will not run with XP. The other (32 bit) applications in the suite can run with XP, like AU, DW, FL, IL, ID, PR.
So, I stand by my previous observation: a reading error on your side, since this is posted in the PR forum, not the IL or DW forum.
As to the Vista question, you can run Vista in XP mode for all those 32 bit applications. Unfortunately it does not run under MS-DOS 6.22 either. I liked that OS.
So that's settled.
XP is supported for 32 bit apps, but not for 64 bit apps.