Agree with T6 and AndrzejL.
Win-anything isn't secure, even if ran in a virtual machine. You will still need to run anti-virus, anti-malware and anti-spyware software, if you want Win-anything to remain secure. However, if your virtual box copy becomes corrupted by any of the aforementioned plagues, you can either just reinstall, or even better yet, restore it from a pristine copy of your virtual machine (provided you kept a backup of your VirtualBox VDI file). Furthermore, any mal-anything that Windows-anything picks up should stay isolated to only that virtual machine, and should not have any ill effects on your host.