Which version of Mcafee did you try to install, I have only tested Enterprise 8i on Vista it had many issues mainly with I.E 7 so changed to AVG Free seems to work fine.
The following link is for Mcafee. If you have recently purchaced a retail copy they provide a link for a download, they will provide a free upgrade for recent new account subcriptions.
http://us.mcafee.com/vista/
Might be worth a look.
scottbelton@tiscali.co.uk