Us non-geeks are always in desperate need of help files!
The Gimp help can't be accessed within Gimp Portable. It's an .exe file that needs to be downloaded separately (over 20 MB) and, when started, doesn't find a registry entry if Gimp is not installed regularly. I didn't manage to make it load within Gimp (a geek or gimp should know how to, though, and please let the non-geeks know!). But, I finally got at the help file anyway. Not bad for a non-geek, eh?
Here's how to: Get an extractor (like "Universal Extractor") and extract with it the gimp-help-2-0.9-setup.exe. You get some file and a folder named "{app}". Click yourself through that folder to your language. The help is there in many .html files. You start out best by double-clicking on "ch01.html", as this is where the help file begins. From within it you can navigate to all the other .html files, e.g. by clicking on the "next" links in each page. That's it.