More and more people are getting phone calls that there are problems with their PC and that the caller can fix the problems. This raises several questions. How do they know your PC has a problem and will they really fix your PC?
The calls may say they are from Microsoft or so other company and that they have observed problems with your machine. They are not part of Microsoft or other legitimate companies. They almost definitely have not observed any problem with your PC and are just cold calling, most often from other parts of the world. If you got one of these calls or get one, consider is your computer even turned on? In several instances I know, no. They also call people with no computer.
Can they fix your computer? First is whether there is anything to fix. They want you to run a program that will then give them access to your computer. Plenty of programs will do this including Remote Desktop Connection and GoToMyPC which legitimate repair people including me use to go in PCs of people we have already worked with and they know we are going in the PC. In this case once you run the program they can access all your information such as bank account numbers, social security numbers, etc. You basically just opened the front door of your house to strangers who said something was wrong in your house and you went shopping while they are there. They may claim they cleaned stuff on your PC but more likely they will leave lots of spyware, viruses etc so they can get more information in future or to use your machine as a bot in doing illegal activity.
In a nutshell, if you get one of these calls hang up immediately, or if you must be polite say no thank you and immediately hang up. As long as you do nothing on your machine they said to do, you should be ok. If you do follow their steps treat it as if your ATM card or other credit data was missing. Immediately notify banks, credit card companies etc and get a legitimate PC person to clean your computer of malware including viruses and spyware.