ARM has a page on this. Windows Embedded Compact 5, 6, and 7 support ARM11.
http://www.arm.com/community/software-enablement/microsoft/windows-embedded-ce.php
I don't think Windows Embedded Handheld 6.5 (AKA Windows Mobile) supports ARM11, but I could be mistaken. I didn't find any information either way.
-PaulH