One of the alternate methods for deducing someone's computer knowledge is to ask them what they do with their computer. The responses may vary as follows, even stereotyped as they are:
"I generally just use it at work." They probably know office applications and enough about the operating system to navigate around, but internet knowledge varies. Many workplaces are now requiring courses that prepare people to utilize a Windows desktop as well as relevant applications for their position in the company.
"I work with them." Not to be confused with the previous listing, this can imply either someone with a Computer Science/Information Science/Management Information Systems/etc. major or someone who has an IT-related job.
"I'm a gamer." They have a fair amount of versing in both hardware and software, and due to the nature of what they do, the knowledge is usually quite current. This varies widely between how long they've been gaming and whether or not they put more emphasis on the performance of the game or the gameplay itself, however.
"I usually just talk to my friends and such." This answer usually implies at least a minor understanding of the internet, and enough operating system know-how to open a browser and communication applications.
"Which computer?" Usually implies a geek, but, be careful, as this can also indicate someone with a machine at work and home.
"I don't use the things." Oh. Well, then. They're telling the truth, but don't scorn them. Using a computer for most people is an acquired taste.