More and more laptops and desktop computers are coming pre-equipped with wireless networking devices -- it's so cheap that they might as well put it in, to have another thing to list in the system specifications. It is easy to tell if a desktop computer has wireless enabled. Have a look at the rear panel for a small antenna. If its there then you have wireless. Laptops a much more difficult to diagnose.
If you're anything like me, though, you probably don't even know how much memory your computers have, never mind whether any of them came wireless-enabled. When you don't know what wireless networking is, it's easy to ignore it in a computer's specifications, and never take the time to set it up and get it working. Here are some things to look for if you want to check your computer's wireless capabilities.
If your laptop came with something called 'Intel Centrino mobile technology', then it's good news for you! Computer manufacturers seem a little bad at explaining what this technology is or does, but it basically means that your laptop has wireless networking built right in, without you needing to do a thing. It is a marketing name for a combination of the Intel Pentium M processor and Intel's Pro/Wireless card.
Your computer should have a 'Centrino' sticker on it somewhere if it is Centrino enabled. If you think you might have taken the sticker off, you can check the name of your processor by right clicking the My Computer icon on your desktop (or in the Start Menu) and choosing Properties from the menu that appears. Take a look at what it says after the word 'Computer' on this screen.
If you're interested, Centrino technology also increases battery life and allows computers to be smaller. Don't worry, though, if you didn't buy a Centrino laptop -- as long as your laptop has a free card slot, installing wireless on it will be no trouble.
If you're not sure whether your desktop computer has a wireless connection, the easiest thing to do is to turn it around and look at it. If a wireless connection is present, you should usually be able to see a small aerial sticking out of the back of the computer, towards the bottom.
If there's nothing there, then it's still possible that you have a wireless device in the computer, especially if you bought it recently and you think you do. It's not a good idea to try to open up your computer just to check something, though, so you should probably try and figure it out using Windows.
Checking in Windows
Instead of fiddling around with your computer hardware to see what you've got, you can check easily enough using Windows' Device Manager. To use it, right click My Computer, and choose Manage from that menu. Now click Device Manager.
You should see a list of all the different kinds of things you can install on your computer. Take a look under 'Network adapters'. Ignore anything that says '10/100' or 'Ethernet' -- they're normal network connections, but not wireless ones. If there's anything else there, it could be a wireless device.
If you think you have a wireless device, but it has a yellow warning sign next to its name in the Device Manager, you should take a look at it to see what's wrong by double clicking its name. Windows should tell you why the device is not working at the moment, and may suggest that you go through its troubleshooter program. Do that before you do anything else.
If it turns out to be a driver problem, you should insert the drivers CD that came with your computer. Of course, as is always the way, you probably won't be able to find that CD -- but don't worry, you should be able to find drivers online. First, you should look on the website of the computer's manufacturer, and then you should try searching for the name that the wireless device had in Device Manager.
Of course, you might find after all this that you don't have a wireless device after all. Hard luck. It's better to figure that out now than to buy wireless equipment and then realise you had some already, though, isn't it? Of course, even if you did find a wireless device in one of your computers, you probably still need more. Don't worry either way -- they're getting cheaper all the time!