How to install new Recovery image from .img file
If you have a fastboot-enabled bootloader version (such as the old 0.76.0000 engineering HBOOT in the EVO's case) you can use that to flash it from a PC via USB. Reboot into your bootloader, then select the "Fastboot" option from the boot menu (if it has one, it may start up fastboot automatically). Once it's ready, go to your PC's shell and execute:

fastboot flash recovery /path/to/recovery.img


You should also be able to use the flash_image binary if your ROM has it (or you install it from XDA). Copy the recovery.img over to your device somewhere then do the following:

C:&gt; adb shell
$ su
# flash_image recovery /path/to/recovery.img