I have a Dell Studio 1737 laptop with an HDMI port. I'm trying to connect it to a 42" Vizio HDTV (brand new). It's worked once, but that's it. Not again. I connect the HDMI cable to the TV and it just says "No Signal!"
I had this same problem. Took me a while but I figured it out. Right click on desktop and select "Personalize". Next click on "Display". You should see "connect to a projector" on the left. Select it then select duplicate. Its that simple.
After selecting video input connection type (hdmi) on hd tv, try right clicking on desktop and go to graphics options. Select desktop plus hd tv or just hd tv. This works with Dell Studio 1555 and Sony Bravia hd tv using the hdmi inputs.