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

Is there a way to change external display settings without being connected the display (Laptop to HDTV)?

• I recently connected my laptop to my hi-def LCD tv by HDMI cable. The first time it worked, cutting off my laptops monitor and appearing on the tv. I could adjust the resolution to make it fit perfectly without overflowing the display (using a 1360x768 resolution, instead of the 1680x1050 i normally use) , The second time I connected however, my laptops screen was cloned, creating duplicate screens. I didn't have a problem with this, but I wanted to adjust the resolution again for the best fit. I attempted this in the NVIDIA Control Panel, when I adjusted the resolution this time, it must have severely slowed the refresh rate, as I cannot see my mouse on my laptop monitor to make setting changes, and the display doesn't register on the TV. When I do attempt to restore defaults while connected, by moving the invisible mouse around, my laptops screen will go black, and not recover. It doesn't turn off, but seems to get stuck trying to readjust. As long as I do not use my HDMI port, my laptop screen works fine, but I would like to be able to connect to my tv successfully again. I have tried rolling back and updating the driver for my GeForce9600m GT as well as a System Restore to a few days before it was screwed up. No luck. Any help would be appreciated. Thanks.

• Answer:

  Get and install the latest driver from HP. If that doesn't work, try to find it on the nvidia.com website. If that doesn't work start your laptop in safe mode, then remove the driver. Restart the laptop, the installed driver will reinstall automatically, but make sure to get the the latest driver from HP before you remove the current driver, so you can install it yourself if needed.