I have successfully enabled Widi on my HP 2740p. I can now wirelessly display the screen output on my LG 47lM760t (2012) widi enabled TV.
My HP 2740P has :-
1. Intel core i5 M 540 CPU
2. Intel HD Graphics
3. Intel Centrino Advanced-N 6200 AGN Wireless adapter
4. Windows 7 Pro Sp1 installed.
Procedure I used to enable WiDi (follow at your own risk):-
1. Download and Install SP56271.exe from Hp website to upgrade Intel HD Graphics driver to 126.96.36.1999
2. Download and Install Intel® PROSet/Wireless Software and Drivers for Windows 7 version 16.11.0 (Wireless_16.11.0_Ds32.exe) from Intel website https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=23723
3. Download and Install Intel® Wireless Display Software for Windows v188.8.131.52 (setup.exe) from Intel website https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=19782
4. Enjoy WiDi
I had the same problem before, although my laptop-hardware meets all conditions I had this problem.
My issue was a second graphic card (HD 4000 integrated plus NVIDIA GTX 675 m). I shut down the nvidia-card, restartet my pc and so in a "HD4000-solo-System" the installation works. After that, the WiDi program found my adapter and i was able to restart my nvidia-card without problems.