These are scam calls, I have had half a dozen of them.
They either
a) Try to get control of your computer (it can be done) and steal personal information off it.
b) Try to get you to sign up and pay for some sort of "computer support" so they can protect your computer (they say).
NEVER do anyting they say on your computer (visit a web site, install a program).
NEVER give them any credit card or bank details.
Last time they rang me I shouted "F&K OFF" down the phone at them. The woman rang back and asked me not to be rude to her !