The majority of high-definition DVDs and downloadable content is copy protected with a technology called HDCP (High-bandwidth Digital Content Protocol). This means that every piece of equipment you use to play HD content must be HDCP-enabled -- everything from the computer to the cable to the HDTV. If you can't play HD content through your computer, than your graphics card might not be HDCP compliant.
Computer to TV Troubleshooting
The biggest problem with connecting your computer to your TV is that, generally speaking, computers and TVs don't display at the same resolutions. For example, the closest thing to the HDTV resolution 720p (1280 x 720) is a monitor display mode called XGA (1280 x 960). Not quite the same. And the closest thing to 1080p (1920 x 1080) is a monitor display mode called WUXGA (1920 x 1200). Again, not quite the same.
The result, in most cases, is something called overscan, where the full computer screen image doesn't fit on the TV screen. Overscan is a bigger problem on SDTVs where the native screen resolution is much smaller than your computer's display. If you're going to use an SDTV as a monitor, plan on lowering your screen resolution to 800 x 600.
HDTVs also have overscan problems, but usually only the very edge of the computer image gets cropped. A bigger problem with HDTVs is when the TV refuses to display a signal that doesn't fit its native resolution.
Luckily, most HDTVs have the ability to scale incoming signals to match their native screen resolution. This involves either upconverting lower-resolution signals in the attempt to bring the resolution up to high definition or downconverting higher-resolution signals for lower-resolution screens. It's not perfect, but for most casual viewers, there's little to no noticeable loss in image quality.
In rare cases, the HDTV won't recognize the resolution of the signal sent by your computer. When you connect an external display to your computer, most graphics cards will automatically try to find a good match for the display's native resolution. If this doesn't work, you will probably need to edit your resolution with third-party software.
Two programs are considered the best solutions for solving connectivity problems between a computer and a TV: PowerStrip for Windows and DisplayConfigX for Mac. Both of these programs allow you to match your graphics card's resolution precisely with the native resolution of your TV. If your HDTV is 1080p, you can go into one of these programs and switch your computer's resolution to 1920 x 1080, even if this wasn't previously an option.
Avoid increasing the refresh rate on your graphics card, unless you have a 120-hertz HDTV. If you send a signal with a refresh rate over 60 hertz to a normal HDTV, you could damage the TV [source: Komando].
For lots more information about home theater systems, follow the links on the next page.