you can upgrade...
mcafee & norton are busters in the first place..
 
I've created viruses that they still dont detect..
now bitdefender is one I cant bypass,.
 
but on your note*
a new install is always best anyways...
but disabling mcafee shold allow you to upgrade from vista to win7 if you want..
no raid drivers or whatever need to be updated/upgraded or whatever
 
i've upgraded 2 computers from vista/xp to win7 with no problem & have done 3 freash installs with win7
...
none of the computers using any anti-virus software
anti-virus is for ppl who don't know what their lookin for..
who decide to click on the 'find a girl friend ad' & end up downloading the setup.exe that they say you need..
lol
 
no-offense,.