Sometimes for older graphic cards only one of the digital outputs supports HDCP. So make sure to use the right one and check that your specific HP display model actually supports HDCP. Check the HDCP status in your NVIDIA control panel. Very likely some of your hardware actually doesn't support HDCP, in rare cases it can be a driver issue. The error message from PowerDVD is quite clear, no clue why you thought updating to version 12 could change anything.
Good luck!

As M8R said, try with all the DVI outputs of the card, here should be at least 2. Some 9600 GT cards (notably the MSI ones) have an HDMI output too though. Also make sure your graphic driver is up to date.

If it doesn't work, you may also want to check the manual of your HP monitor to see if it is HDCP compatible.

Other things you can try:
- Revert your DVI cable (put the plug of the monitor into the PC and vice versa). No kidding, that works sometimes.
- Try a different DVI cable.
- Try the HDMI output of you have one (with an HDMI to DVI converter at the end, monitor side).
- Try HDMI with two converters.

- Last solution (albeit a paid for solution after the free trial) is to use AnyDVD HD which will disable all those protections. If your monitor isn't HDCP compatible, that may be the only solution. I'm using it myself because my audio card doesn't have that famous "protected path" and would otherwise not be able to playback 24 bit HD audio.

What's the brand (manufacturer) of your graphic card?
And the references of your HP monitor?

PS: it's always sad when protections become a nuisance for honest consumers My collection: http://www.blu-ray.com/community/collection.php?u=194008&action=showcategory&category=1&categoryid=7

Like the user before has mentioned, use Slysoft's AnyDVD HD