Making an OS, Problems

Hey guys, I am kinda new to the whole ComputerCraft stuff, but, I was watching this tutorial (https://www.youtube.com/watch?v=XPpMkDfzwB8) on how to make a simple and easy operating system. It was all going fine until it told me: "bios:339: [string ".menu"] :81: '=' expected", this didn't happen to him in the video and I have no idea where I went wrong. Please help me if you can, Thanks.

Please post your code.

With no code my best guess is you misspelt some keyword (for, return, ect) so instead of a keyword you have a variable name which it expects you to give a value.