I. Before You Begin
1. The only reason to unroot a phone is if you have to send it back in for warranty purposes. Otherwise just try loading a different ROM instead…
II. Get Back to Out of Box State
1. Download HTC Sync (if you don’t already have it) and the Original RUU and save it to your computer.
Original Desire RUUs (Choose the best one that suites your specific device) Thanks Jesterz @ XDA!
2. Double click the HTC Sync program and install it.
3. Plug your phone into the computer via USB cable and select HTC Sync when prompted on the phone on how it should connect.
4. Double click the RUU exe you just downloaded and follow the prompt to restore the phone back to factory settings.
Issue: After the RUU tries to reboot my phone into bootloader, it sits at Waiting for Bootloader and eventually gives me an error.
Solution: Simply unplug the phone and plug it back in (leaving it on the HTC logo screen), and run the RUU again with it in that mode already.
Issue: After the RUU says sending and updating signature, it brings up an error saying use the correct RUU for this device.
Solution: Either find a different RUU for your phone, or just put your Goldcard back into the phone and start over.