I'm not exactly sure what you're experiencing that's not working, but let me tell you how I hook up my HP DV2 Notebook to my Sony HDTV via the HDMI wire.

In three words.

Just Hook It Up.

Oh, wait, that's four. :-)

I'd suggest you start by unhooking the monitor and rebooting. Then hook it up again. When I plug in the HDMI cable on the HP laptop, I promptly see this:

If I do nothing, the display that's on the TV is mirroring what's on the computer screen. (Mirroring means that you get a duplication of every element: what shows up on your screen also shows up on the second screen, including the task bar, desktop icons, warning messages, and everything else)

If you're not seeing this behavior when you plug in the second monitor, then you might need to have your computer "detect" monitors after you've plugged the second screen in. You can do that by following this path:

Get to the Control Panels by clicking on the Windows icon in the lower left corner and picking "Control Panels" from the pop-up menu. Now choose "Appearance and Personalization":

Step in one more level by clicking on "Personalization":

Ah, finally, click on "Display Settings" (the bottom option on the list) and you should see:

Here you can see I have a second screen hooked up (screen 1 is always the computer itself) and that the second screen is "to the left" of the main screen (which is important so that I know in what direction I should drag windows to get them to the TV screen).

If you don't both monitors shown here, click on the "Identify Monitors" button and see what happens. If that doesn't work either, I suggest you try either using another computer with your TV or a different second monitor, to see if you can isolate the problem.

Good luck!