No. If your stock all you need to do is download the .exe file. After its done downloading double click on the file and it will guide you through the setup process. There is no need to rename this file to pg051img. It utilizes HTC's software, all you need to do is plug your phone into your computer with the USB cable and follow the directions.
Most people reccomend using the .zip file to update from what i've seen. Just rename it, put it in the root directory on the SD card, boot into bootloader and follow the on-screen prompts. Its pretty simple. I did 2 RUUs for the MR2 updates. Its easy.