They claim to be from Microsoft, that they've receive an error from my computer.  I suppose they were going to instruct me to follow some steps from my system.  I declined.

IT IS A SCAM!  Microsoft has a warning on their website about these types of scams:

http://www.microsoft.com/en-gb/security/online-privacy/avoid-phone-scams.aspx

Do not let them have remote access to your computer.  They will extort money from you and install malicious software that will allow them to steal your logins, passwords, credit card numbers, banking info and any other personal information that may be on it.

I looked up their site and got a link to 411.ca.
Don't respond to it or give your Facebook, Google or other information for verification to make comments.

This could be part of their scam too.
I made a comment and got locked out and had to reset my Google and Facebook passwords!