I've got a laptop running a Core i7 2720 as well as an NVIDIA GeForce GT 555m card. Perhaps I don't understand this as much as I should, but it seems to me that nearly every graphical aspect of my laptop depends on the onboard graphics provided by Intel. Anyway, I'm having trouble connecting to a TV via HDMI (an Insignia 26'' TV). When I have the HDMI cord connected to both places and the input correctly set on the TV, I cannot use the TV as an external display at all. Nothing works - Windows key + p, NVIDIA control panel, Intel HD graphics control panel, Win7 "Screen resolution" - none of these can configure the external display even though the TV is definitely connected correctly. Strangely, when I change the TV's input to accept the other HDMI input (which is connected to a cable box), the laptop magically finds the TV and gives me options in the NVIDIA control panel and in Windows 7's "Screen resolution" options. Intel HD graphics control panel still doesn't provide any options for external displays at this point, which makes me think Intel is the weak point. Even so, the options available are entirely useless because it's not like the TV is in the correct input mode - it's not, but my laptop can still detect the TV. At this point, if I switch back to the correct input mode on the TV (the other HDMI input), the laptop's graphics are exported to the TV for about 10 seconds, then it pretends the TV is completely disconnected even though I haven't touched anything.
To further my belief that the Intel HD graphics is screwing things up, I tried connecting to the TV via HDMI, making sure the input was correct on the TV (the connection is correct at this point), then disabling the "Intel HD Graphics Family" display adapter in Device Manager. Sure enough, the laptop immediately projects graphics up to the TV - my guess is that the 555m card takes over at this point and actually works, but I'm not sure why it works.
On top of all of this, my laptop was able to connect to this TV last week just fine. I think I had to restart to get it to recognize the TV when I tried it (which none of my other laptops have to do), but it was working, and I've changed nothing since then. Just now, I've updated the drivers, getting them from Intel's website, but nothing has changed. I've searched around and seen issues with the latest driver and some TVs, but it's not the same as my issue.
I know this is complicated, but does anyone have any idea what's going on? Any ideas on how to fix this mess?