We need to turn off one of HTC's defaulted on features. It is the very frustratingly named 'Fast Boot' in Settings > Power. No, this is not 'fastboot' in the Android SDK. This is a feature that is like Hibernate in Windows but for HTC devices. I really hate how HTC calls it this, but that's what they decided to call it.
Next, go to Settings > Applications > Development and check USB Debugging. You'll need this enabled for the adb reboot command. Plus a number of rooting apps require it. Give the computer a few minutes to recognize your phone, install drivers, and so on, if it needs to.
Connect your phone to your computer. From now until you're done flashing your ROM, you will not disconnect the USB cable. So don't even think about it!
Quick tip: Do NOT connect to a USB 3.0 port. For some reason, fastboot will not detect your device if you're connected through a USB 3.0 port. If you're unsure if you have a USB 3.0 port, don't worry about it unless your fastboot commands say that they're waiting for device when the device is hooked up.
Now, in the command prompt, type (or copy and paste):
Code:
adb reboot bootloader
You should now be in your bootloader. It should say "FASTBOOT USB" in red highlight. If so, this is good! If not, make sure HBOOT in the menu is highlighted and push the power button. This will change it to FASTBOOT and it'll detect that it's connected to USB and change in a few seconds.
Now type (or copy):
Code:
fastboot flash recovery recovery.img