How do I get the RUU Update Utility for the HTC Inspire?

Hello, I am a BRAND NEW Android user. I bought my HTC Inspire from eBay and it cam rooted with the stock version. I wish to unroot it so I can update the firmware. I have no idea what "flash" a ROM or anything means so I just want to unroot it. So I'm trying to use the method that uses the RUU Update Utility but I always get an Error Message 130 stating that I have the wrong RUU version for my phone. So where do I get the correct version?