don't call that 800 number back!

I still see far too often the case where users see a message that pops up on their screen saying - Call this number to clean your pc.  I say one word - NOOOOOO! 
You have to be more cautious than to 1) call some random number and 2) let someone you don't know give you any guidance on your pc.  It's synonymous of driving down a road and having a stranger flag you and you simply pull over and say - GET IN.  Of course you wouldn't do that.  The next time you see a message pop up on your screen saying to dial a number - DON'T CALL THEM BACK! Call Us - your local reliable and reputable computer service provider.