I don't find too many torrents of products like Kapersky and end up buying it. The torrents tend to be of old versions. Plus, I wonder about someone splicing in malware. I tried AVG Free and was not impressed. Is it best just to buy your antivirus software?
Download setup files from publisher's website then google for keys Kaspersky keys have a short life and get blacklisted quickly, so i suggest you download Eset and google can help you with the rest
Forget retail products. Go with Symantec AV Corporate or newer Symantec Endpoint Protection. Install as un-managed client. These work well, require no key for install, and Live update never times out. Only negative feature is that for x64 OSs, can't do an Explorer right click & "Scan for Viruses...."