Free 8 install advice for Vista x64

Is there a best way to install version 8 free on to a Vista x64 machine? Should I use the Maintenance page link, download the .exe, clean install?

Second, how long will version 7 work and what security enhancements make 8 better than 7 other than the software updater?

Thanks as always.

I installed Avast free on a VM running Vista with no problems. I uninstalled the old version booted into safe Mode and ran the Avast uninstaller then rebooted and right clicked on Avast and selected run as administrator and it installed fine.
Joe

For x64? If so, thanks.