Win XP work with Opus 11. I'm most concerned with the use of Float Tool Bar.
Bob
Opus still works with Windows XP, but it really is time to stop using Windows XP for other reasons. It is no longer safe to use Windows XP because Microsoft are not releasing security updates, and development and debugging tools are dropping support for it, which will make it difficult for everyone to continue to support it with their own software.
I run Windows XP in a virtual machine on my Linux box. It runs much better than Windows 7 or 8 in that type of setup. Booting that VM up is lightning fast. (Plus, I don't have to buy another Windows license.)
Windows XP has it's uses still. Though, it's behind multiple firewalls.
Windows 95 boots even faster. 
It's time to move on, Windows XP is dying and will soon be more difficult for everyone to support than is worth the effort for the handful of people still using it for whatever reasons.