My 2nd "screen" (HDMI) must be forced each time windows starts

Hello,
I have a MSI Radeon HD7850 graphic card. I plug the DVI out to my monitor (for video only. this allow a resolution better than 1080p) and my HDMI out is plugged to my AV receiver (for audio only : this allow DTS HD / Master audio).
This configuration was OK with my previous ATI graphic card.
But now i have a little problem : each time i boot windows, the HDMI signal is received by my AV until end of windows logo, then, most of the time, no signal (of course i still have DVI video signal to my monitor). To solve this i must go to windows "screen resolution" menu, and activate 2nd display via "extend my display".
I don't understand why this setting is then lost after shutdown.

Note 1: when i have changed my graphic card i have cleaned old drivers (into safe mode).
Note 2 : i can also extend monitors doing a "C:\Windows\System32\DisplaySwitch.exe /extend" call