It's a well-known scam.  Ask for a chapati recipe if they call back -- that's what I did.  They weren't happy with me. 
Hello, I recently purchased an inspiron 3000.  I received a phone call from a guy that said he was from techzone us and worked along with microsoft.  He said they showed my computer had trojans/malware and he could help me fix it.   I have Norton 360, but he said it would not fix the problem. I just took down his name and number and told him I would have to call him back.   Does this sound legit? Thanks!
TechZone US Spam?