Actually, the safest way could be 'wubi'.

From their site:
"Wubi is an officially supported Ubuntu installer for Windows users that can
bring you to the Linux world with a single click. Wubi allows you to install
and uninstall Ubuntu as any other Windows application, in a simple and safe
way. Are you curious about Linux and Ubuntu? Trying them out has never been
easier!"


http://wubi-installer.org/