I think that there is an inherent problem in a question like "How much do you know about computers?". Well, what do you mean? Ultimately, "computers" comes down to hardware, but there are many layers between hardware and the end result that you see on your monitor, screen, hand-held, etc. If you say "How much do you know about software engineering?" or "Networking, network engineering, programming", and so on, that is more specific. But "programming" is in and of itself somewhat nebulous. Essentially, it comes down to a paradigm of realizing problems and challenges, and finding logcially structured solutions to such. How you do that depends on what you're trying to do, and what language(s) you're using to get there. You wouldn't use PHP for system programming, and wouldn't use Assembly for web development, etc.
Personally I would say I know a fair amount, but not a whole lot. I can program in C++, PHP, and Python a bit, as well as a little bit of Perl. I also am familiar with Tcl, shell scripting, MySQL/SQL, and of course markup/styling like (X)HTML and CSS. I am usually pretty good at troubleshooting, mainly on Linux or other UNIX/BSD based systems. I think this is in part because I spend a lot of time understanding how things work, and to me, Linux is wonderful for that. I would actually consider Linux a way of approching computing than an OS (which holds some truth, it is a kernel, not a complete OS). I've built several computers, and know a fair amount about hardware, but more about software. I wouldn't consider myself to know a lot in either, but I do know a decent amount. Really, the more you delve into any field of Computer Science, the more you realize you don't know. There's always something to learn, and I think that makes it really fun. You always find out something new when you go play around with computers.