[HELP] How to reset my HTC 6950 back to Sprint ROM?

[dabura]

Hi, I recently bought an HTC Touch Diamond from a friend of mine, it come with a custom ROM installed (MightyROM). I brought it to 4 different MetroPCS store to get it flash to their network, but none of them were able to do so, and have no reason why it didnt work neither. The corporate store were able to recognized the phone and were able to run Houdini to flash it, but it stopped half way with a big FAIL message. I went to Houdini Support and was told it might be the custom ROM that is the issue, and told to restore back to the Sprint stock ROM. I have no idea how to do this, and the rep told a Hard Reset will not restore the stock ROM ( he said the ROM is like an Operating System, and will need to be reload). Can any one help me out on this? Thank you very much and any help is welcome