Radio works now, with either HTC Headphones or the 4-1 block and your own 2.5mm or 3.5mm headphones.
If the sound doesn't start right away, click on the headphones and it should work.
Use this file:
FM Radio Made by me!
Here are the instructions:
Navigate to OEMDrivers folder.
Delete FMS.dll Folder
Delete FMS_api.dll Folder
Copy loose files into OEMDrivers.
Copy Multimedia - FM Radio 1.6.1816.4032 to OEM Folder
Flash!
You'd better say thanks...
Also, you can donate to no2chem and myself
Edit:
I'm not sure if it will work or not... try this:
Didn't Work
Thanks to Lenny, JD and no2chem for all their work on this!