Here is a link to an actual Microsoft page with a warning about these scams:
http://www.microsoft.com/security/online-privacy/avoid-phone-scams.aspx
Here is another link that describes the CLSID scam. The number that they give you is common to all Windows computers.
http://www.welivesecurity.com/2011/07/19/support-desk-scams-clsid-not-unique/