1) factors suggesting it's a scam
Unsolicited contact- no company would usually ever contact you regarding a personal issue you have not contacted them about.
General calls lacking specifics i.e 'about your computer security' or 'from windows'
Either asking for common personal security information i.e mothers
maiden name, date of birth or address or windows password
(possibility of you using common passwords) or leading you to create
a remote logon session so they can 'fix' your computer which is actually software to record activities you perform, i.e online banking.
Pop ups onscreen on computer, leading to malware as above.
3) Things you should never do
Respond with any information to an unsolicited approach