Just a warning. I've had a few people ask me about some random phone calls from a guy in "tech support" telling them that they have a virus, and asking them to let them fix their computer.
HANG UP ON THEM, or string them along for fun (like have them walk you through what they need on your Windows 3.1 computer), but DO NOT, I repeat, DO NOT do anything they ask. Just stay away from your computer altogether in case you're tempted to do anything silly. THIS IS A SCAM. They will take over your computer, and they will steal any and all information you have on it. If you don't pay for tech support, then you don't get tech support. Hell, anyone who has tech support knows that even if you do pay, you don't really get tech support!
Instead, get a good Anti-Virus program. You can buy one like Norton or McAfee. Another great option for Windows is Microsoft Security Essentials. It's free, and I have found it very good and up to date. Download it here: http://windows.microsoft.com/en-CA/windows/products/security-essentials
Also note, Mac users may be safer, but not completely immune. They can just as easily take over your fancy Apple computer if you let them.
If you know you have a virus, there are other things you can try, like the online scanner at Trend Micro - http://housecall.trendmicro.com/ - You will have to download a small file to run it, but it is good at cleaning. Please note, this is not an anti-virus program, it just tries to clean your computer, so you should always have one of the above programs running too.
1. Do not download anything from a source you are unsure of.
2. If you don't know what you're doing, stay away from Bittorrents! Yeah, I'm talking to you pirates out there. Whenever a friend asked me to help them with their computer, the first thing I looked for was a program like Limewire, or uTorrent, and once I saw one of those, I knew instantly that I was in trouble. Most of the time I just wiped their computer to teach them a lesson.
3. These hackers and spammers may be bad people, but they are extremely clever. NEVER click on a link in an email that seems suspicious. PayPal will NEVER email you with an e-mail that says "Dear Customer". If they do email you personally at all, they know your full name. Apple is also not giving away thousands of iPads because Steve Jobs died. A good trick is to hover over any links in an e-mail, you should see the link appear at the bottom of your e-mail program. The link should be some weird name (note, it could have the name of the institution in it, like http://paypal.thisisascam.com, the actual website is the last part, the "paypal" part means nothing). Be smart about things, use common sense, and remember, nothing is free.
4. Spammers and Hackers feed on a variety of things: ignorance, trust, greed, fear, so keep those in mind when you get anything in your e-mail or over the phone.
5. Never give out personal information, and DON'T keep your passwords in a text file on your desktop called "mypasswords.txt". You can use a password manager program like some of them seen here: http://lifehacker.com/5529133/five-best-password-managers - I use one called Pocket, that syncs with my phone over DropBox, so that I have them anywhere I go.
6. Use common sense.
Has anyone else gotten this phone call yet?