On my laptop I used the HDMI once to connect to my TV. It worked fine once I changed the display setting to TV, and showed my screen on the TV instead of showing it on my laptop screen. Then I pulled out the HDMI cable the laptop screen stayed blank. When I plugged the HDMI cable back in both TV and laptop stayed blank. I tried pressing the button on the keyboard that says HDMI/LCD but it did nothing. I tried it with the HDMI plugged in and not plugged in. I also tried windows+p. Every time I turn on my laptop now it shows on the screen that windows xp is loading then it's blank. If I start it in safe mode it works but I can't open the NVidia control panel in safe mode. I also tried plugging in a different monitor with different HDMI cable and both screens are always blank. What do I do?
Using HDMI involves something called 'Digital Rights Management' (DRM) ... this is designed to prevent copying of data from a HDMI cable .. unplugging it may have 'tripped' some stupid DRM 'trap' ..
First make sure you have the display drivers to hand (ideally 'unpack' them to your hard drive in some easy to find folder)
Then, (in safe mode) un-install your Graphics driver ... reboot to 'normal' mode and you SHOULD get the 'default' MS Display Driver (which likley shows a low resolution 640x480 VGA screen) .. and from there re-install the real driver ..
I had a same problem when I used HDMI, I think it's because there's no active process running OR your graphics driver is screwed up. Here's a solution that might work.
Press Ctrl + Alt + Delete and select Task manager. Under Applications select New Task. Type in explorer and press Enter. You must see your background image, taskbar and icons.
Hope that helps otherwise re-install your graphics drivers.