Learning how to use a computer just requires curiosity or a bit of bravery. Most people I have seen who struggle with computers lack either or both. They are either not curious enough to try to click something they don't know about to see what happens or they are afraid they'll break something.
So what I like to do when I'm helping someone out is set up their computer so that they can't easily do something bad. So I setup an admin account with a password, then setup a regular account and tell them to only use the regular account. This way, they can't easily do stuff like delete all the windows files and if they get a virus or download spyware it can't do much damage.
Then I setup their desktop. Usability on the desktop comes down to something very simple at it's foundation: options. If there are 100 different things to click on the screen, it's harder than if ther are only the 10 most important things.
So I clean up the desktop. I get them set up so that the only icons on their desktop, their quick launch, etc are the ones they will use the most. I also change any default settings to the most optimum setting for the user (e.g. larger text or icons if needed, lock taskbars etc) and get the user set up for security (anti-virus installed and working, removal of whatever bundled test AV program came with the computer, operating system updates set to automatically update security fixes, etc).
So for example, a while back my grandmother (well into her 80s) wanted to ditch AOL dial up and get DSL. So I set up a gmail account for her and setup Outlook Express to get the email and walked he through the basics. I installed firefox for her, made it her default browser and setup the desktop and quicklaunch icons. I set the home page of the browser to a search engine, and showed her how to bookmark sites.
I also showed her how to listen to her music on Windows Media Player, and to rip CDs, but the ripping CDs part didn't stick.
But all in all, she used it very well. I had it setup pretty cleanly so that the couple of things she already used on computers were easy and accessible, and though she had trouble later with things like ripping CDs or exploring the rest of the computer she didn't have any trouble with the very basics of email, internet browsing, and music (oh, and the couple of windows games she liked playing).