I just received such a call this week! Since I use a Mac I knew what was going on. I work remotely on a vpn so I know better than to give information about my work pc over the phone, for example! I played dumb and strung the idiot along, telling him that I didn't know much about computers and he'd have to wait until my son got home - I tried to get a call back number but he wouldn't play. He actually called me back later to check if my son was home!
I figured it was better to mess with them, because at least they aren't spending time with someone they COULD scam...