When a virus is detected during an installation process, but not on the program CD - is it a false detection?

This is a general question about how Anti Virus software perhaps falsely detect virus signatures. My problem is this : during an installation of a specific program, McAfee comes up with a virus detection alert. A specific file is beeing mentioned as a contaminated file, with a specific virus name. But the strange thing is that the virus is not detected while the program-cd is searched - neither does the installed program folder contain any detected viruses.

I have searched on the internet for furher information about this virus, but I havent found anything useful - other than it exists, and that it is known by all the big AV-softwares. I havent found anything about false detection beeing triggered.

I have searched the cd, and installed programfolder also with other AV-software without any success. I am starting to lean towards to that McAfee is mistaken, and falsely reqognizes some aspect in the installation process as a known virus signature.

Can one be SURE of that the program-cd in fact does not contain a virus, if the same antivirus software which detected a virus during install, does not detect it before or after on the program-cd or installed files on the computer?