I don't answer unrecognized phone callers.  If they don't leave a message, they don't deserve a call back.
This call ID'd as Minnesota.  No message was left.  It could be someone harvesting valid phone #'s.  It could be a political call (lots are coming in now). It could be a con artist.  It's probably a robo-call.

Called me at 7 AM.  Had my name and identified himself as "Windows Technical Dept calling me about my computer."  I have a Mac and don't run Windows OS.

Fake computer tech scammers.
They want to get you to allow them to remotely access your computer to "fix" the errors your computer where sending them.
They actually will install trojans and then make you pay to have them removed.
See:
http://www.consumer.ftc.gov/articles/0346-tech-support-scams
Hang up, report them to the FTC.