You can download all the intel driver from here : i don't touch anything from now beacause i'm very happy that i've miracast working on windows 7 ! :) may be also that some step have cleaned the registry.
I think that in some case installingÄirectly the 4.2.29.0 after uninstalling the previous version may be that work.
The strange is that from the preinstalled version, when i've done the upgrade with the "intel widi update tool", the version goes to the same 4.2.29.0 but don't works. Tadah! it work like a charm !! fast and real stable connection to the projector ! = from now it's the correct procedure = uninstalled the widi from the ultrabook and restarted installed the latest 3.0.13 version (installing the 6.* intel say that the version 3.0.13 was the latest supported by the hardware - false!) doesn't work ! Upgraded with the "intel widi update tool" to version 4.2.29.0, restarted and.
Removed and installed the latest (widi 6.0.62.0) doesn't work (to be exact complain that the hardware it's not supported by widi - strange but false !). Upgraded with the intel widi update tool, doesn't work. With the widi version preinstalled doesn't work. The key in this case was the correct version of the driver (latest for the graphics card, latest for wifi card) and a correct procedure (a nightmare!) for the widi software from intel. I would let you know that i did this successfully from a Windows 7 ultrabook (asus zenbook ux32vd) to a miracast