Did you just get a call from a pleasant sounding person with a foreign dialect letting you know that they have detected errors on your computer? They'll even offer to show you what is wrong and 'fix' it for you.
You've just become a target and potential victim of a PC Support Scam. This scam is known by many names, It's been called the Fake Tech Support Call Scam, The Event Viewer Scam, The Ammyy Scam, and The TeamViewer Scam (the last two names denote the name of the legitimate remote connection tool used by the scammers to connect to and take control over your computer).
This scam is global and has likely bilked millions of dollars out of victims worldwide. The scam has been around for several years and doesn't appear to be losing any steam. If anything it seems to be becoming more prevalent, with new variants cropping up everyday,