Here is how I solved my modem on high definition problem.
First I had a HP Pavilion Laptop DV1738od with Windows XP Media Edition.
1. Make sure to undelete any modem software currently installed.
2. You need to install Universal Audio
Architecture driver first before install the sound card
3. When the system detects new hardware (the modem), allow it to connect to the internet (you'll need to be connect via network adapter or wireless for this to work) one time.
4. It should be able to detect the correct modem driver and install. (Mine found an HP Modem and installed without any more interaction from me.)
Hope this helps someone with the same problem. Key is to delete any existing modem drivers.