iTunes Error Message 54 I ran into iTunes error message 54 when I was attempting to backup my phone. I have an iPhone 4 with iOS 4.2.1 that I'm trying to update to iOS 7.1.2.  I am currently on Windows 10 operating system with the latest iTunes. I need step by step instructions please.
Step one - https://support.apple.com/en-us/HT205597 - following all the links - especially on a PC might take two hours or more depending on how good you are with troubleshooting security on PC OS.
Step two - get more logs/detail - take notes of the articles above in case you didn't do what they asked and instead did what you thought was correct 
Step three - ask a follow on question or contact Apple support with the "more logs"