It's always advised that you uninstall any existing AV or IS product prior to installing McAfee (or any other AV/IS for that matter).
However, because the installation process uses a download manager (and must be on-line), isn't your unprotected system vulnerable to attack while the download/install takes place?
Much better to be able to download the complete McAfee product, go off-line, uninstall the old AV/IS and then install McAfee (at least up the point of activation).
Is it possible to download a McAfee product without using download manager?
Can the download manager download to the hard drive for later installation off-line?
I know McAfee are not the only company to use a download manager, but there seems to be a security loophole here.
Any thoughts welcome.
No it's not possible but there isn't much risk as long as that is all that is being used at the time, advisable in any case. You can always enable Windows Firewall in the meanwhile to afford some temporary protection.