My Windows 98 computer had a totally generic icon in place of the usual "My Computer" icon for a year or two. I thought I'd done something bizarre to it, and assumed it would be a royal pain to fix, involving registry hacks and the like.
So I downloaded the Windows Power Tools, even though they're supposedly only for Windows 95, and they didn't do what I wanted. So I poked around a bit more and discovered on the Screen control panel, there is an Effects tab. I'd only used it to turn on font smoothing, as I recall, and that was where you changed the icon. Not hard at all.
A trivial instance to be sure, but this brings up learned helplessness. You learn that you can't do something, and if you believe you can't, well then, you can't. It's completely different from not knowing whether you can or not, which allows you to find out.
The canonical example is elephants. According to the possibly apocryphal story, young elephants are chained up with strong iron shackles. They learn that they can't be broken, and by the time they're an adult, a simple rope restrains a grown elephant that could easily snap the rope from trying to get away because they know it can't be done.
While the elephant story verges dangerously close to an inspirational poster, I've found it a useful metaphor. There have been a number of things in my life that I have been convinced I could not do. Once I was able to move myself to the "Well, I may not be good at it, but I may be able to do it" frame of mind, progress usually followed. Examples include losing 100 pounds, dating, and, more recently, cooking. (Although I still maintain that forgetting aluminum foil was pretty funny.)
Many people have developed learned helplessness toward computers. Otherwise competent people suddenly say, "Oh, I don't know a thing about those computers." The very smart Phil Agre pointed out that the way computer users blame themselves for computer problems bears a disturbing resemblance to the way victims of domestic violence tend to blame themselves (usually with the help of the abuser) for the violence.
This applies to technical and usability difficulties. If I just weren't such an idiot, I wouldn't get hit with the blue screen of death. If I weren't such a space case, I wouldn't lose that email I'd been writing for an hour.
As in life in general, it's hard to break out of a cycle of learned helplessness when it comes to computers. Some time back Phil Agre wrote a great article called How to help someone use a computer that provides excellent advice for experienced computer users when they help less experienced users. I make it a point to go back and re-read it from time to time. I don't think the summary on his main page where he links to the article—"help helping people use computers without oppressing them"—overstates the case.