I noticed this thread a while back, but usually when your computer gets to the point where it displays "DSMOS has arrived" and it gets stuck there, it means you have a graphics issue. At this stage all the kexts have been loaded but you get stuck here because OS X doesn't know how to properly display an image.
There are two things here you have to understand. Since your computer has 2 graphics GPUs, one being ATI Radeon and the other one being Intel HD Graphics, some users have the ability to change their primary graphics in the BIOS. If you do have this option, then I suggest changing it to ATI Radeon. From here, you will obviously have to find compatible kexts for it.
On the other hand, if you cannot change it in the BIOS, then from what I'm seeing is that your computer is currently booting using the Intel HD Graphics GPU. You cannot have the Intel HD Graphics kexts inside the USB installer. You have to take delete them manually from /System/Library/Extensions or else you will never be able to boot.
So in other words, your HP 4720 works fine, you just need to see what GPU is available in the BIOS, if there is even an option in there.
