Why can't I duplicate laptop's screen to HdTv?

Why can't I duplicate laptop's screen To HDTV?

• The day before yesterday I bought 2M Sm@rtCom HDMI cable and succeeded duplicating laptop's screen to LG HDTV. Yesterday I tried again but this time the option for duplicating screen did not show up and I could only extend the screen: I tried playing with resolutions, connecting to HDTV and then starting laptop, switching between HDMI cable's ends - all to no avail. The option disappeared. There was another option but it made 1|2 multiple screens in my laptop's screen to appear and nothing on HDTV. UPDATE: It seems that do not have option to duplicate at all. Today I connected again but to different HDMI slot and screen appeared successfully on both laptop and HDTV: However when I clicked on "Identify", both HDTV and laptop showed number 1. Shouldn't it be number 1 and 2? I cannot change resolution by the way since the laptop's 1366x768 screen is cloned so it is a little wider than HDTV can handle, but still viewable. HDTV can handle a maximum 1360x768 but not 6 additional pixels. It can handle Full HD however. It seems that Intel HD Graphics outputs HDMI while nVidia outputs VGA. DELL Latitude E6420 Intel HD Graphics with nVidia NVS 4200M Windows 7 Enterprise

• Answer:

  It seems that Intel HD Graphics outputs HDMI while nVidia outputs VGA. That's indeed the only way to explain both screens are "1". There will be some software built-in somewhere to manage this switching. Try: Dell's graphics drivers instead of Intel's/nVidia's ones Installing http://support.euro.dell.com/support/downloads/download.aspx?c=en&l=en&s=bsd&releaseid=R312259&SystemID=LAT_E6420&servicetag=&os=W764&osl=ge&deviceid=21360&devlib=0&typecnt=0&vercnt=2&catid=-1&impid=-1&formatcnt=0&libid=60&typeid=-1&dateid=-1&formatid=-1&source=-1&fileid=472072 Installing http://support.euro.dell.com/support/downloads/download.aspx?c=en&l=en&s=bsd&releaseid=R312092&SystemID=LAT_E6420&servicetag=&os=W764&osl=ge&deviceid=27394&devlib=0&typecnt=0&vercnt=2&catid=-1&impid=-1&formatcnt=0&libid=7&typeid=-1&dateid=-1&formatid=-1&source=-1&fileid=472009 The last two packages do some hardware control stuff, maybe they include the code we're looking for. Did you try to disable nVidia Graphics (or Intel's), are you able to mirror the screen then?