VirtualBox is perfectly capable of running multiple operating systems. It can also run harddisk images of other visualization software without conversion. There is no visualization software that comes as a single program and will give you all kind of os's to work with. Due to licensing and other restrictions this is simply not possible. You need to provide the images yourself (although a lot can be downloaded pre-installed).
Virtualbox even provides you images that can be readily downloaded for some operating systems. Check it out:
You won't find windows on the website above, but microsoft provides some vhd's themselves you can download. Check it out: