Failed Security Update

Purchased a Norton antivirus update for my computers as I do every year.  When I went to upload it to my  desktop, received the following message:   

Your key has been redeemed successfully but the setup could not be started.

The error occurs because of out-of-date Operating system components related to XML Core Services (XML). XML is a set of services that allow applications written in JScript, VBScript, or Norton development tools to build Windows-native XML-based applications. We recommend you to CALL us 1800-881-0552  in order to fix it.  Called the number and a gentleman who I could barely understand accessed my computer and said I had a  slow computer and needed stuff cleaned and then went into a 1 to forever years contract to keep it cleaned.  One year was almost $200.00.  All I want is for the Norton antivirus to load properly like it has for years.  Should I do this (hope not(, take it to my tech guys and have them "clean" it, or just shoot it and buy a new desktop.  I'm too old for this junk.  Will McAfee work, would rather stay with Norton, but may not be worth the sudden hassle.  Thanks.... Mac