This is the file /system/usr/keylayout/supersonic-keypad.kl that contains the hardware key mapping. To disable a hardware key, simply remove or comment out the entry in this file.
Here is a copy of the HTC EVO key mapping file.
key 107 ENDCALL WAKE_DROPPED key 116 POWER WAKE_DROPPED
key 115 VOLUME_UP WAKE key 114 VOLUME_DOWN WAKE
key 217 SEARCH WAKE_DROPPED key 158 BACK WAKE_DROPPED key 139 MENU WAKE_DROPPED key 102 HOME WAKE_DROPPED
Just upgraded my EVO 4G from "VirusRom" to "Sprint Lovers" ROM. This ROM is based on the latest HTC build (3.70.651.1) with the stock kernel. While upgrading the ROM, I also upgraded all firmwares. Here is latest software version on my EVO 4G.