I. Before You Begin
1. The only reason to unroot is if you are sending it in for warranty purposes, otherwise just try to flash a different custom ROM…
2. If you feel you still need to downgrade, this method will get you back to the stock firmware that came on your device.
II. Downgrade Back to Stock Using the HTC RUU
1. Download the RUU
2. Plug your phone in via USB and mount the sd card so we can transfer files to it.
3. Copy the PB31IMG.zip file to the root of your SD Card (NOT in any folders, just on the SD Card itself).
4. Unplug the phone.
5. Turn the phone off.
6. Turn the phone back on by holding down Volume Down and Power until the Hboot screen comes up.
7. It should automatically find the .zip file we just put on it and ask if you want to update. Choose Yes.
8. Once it is done updating, you are back to the stock Incredible firmware.