I also sent a support request to Microsoft Xbox support via their web site. Here's why I said:

"Hello, I'm trying to locate the correct Xbox 360 universal remote control IR code so it will control my HP TV. Your web page doesnt list the code for Hewlett Packard. [Link: xbox.com]
I have the HP LC304010. The HP web site lists the advanced IR details/ discrete codes for every button. [Link: h10025.www1.hp.com]
Could you please forward this to someone that could help me match my tv's code to one that might work in the remote? Besides trying every Philips code, I also tried the channel up/down method to see if the TV would turn off. It never did after many many presses. Please help!"