I decided to uninstall ASIO4ALL for testing purposes and use the realtek driver as the output for Pro Tools. Unfortunately I'm faced with the same problem with not being able to playback windows sounds at the same time as running Pro Tools. Rather frustrating as I'm wanting to go through a Pro Tools video tutorial..
I came across this link, maybe it could be the work around?
http://odeus-audio.com.au/Odeus/AsioLink