This is probably not of much interest as I believe that myself and BB are the only members using virtual machines but it is still good info... I think.
I am sort of making a history of Windows through virtual machines on my main system. So far I have Windows 2000 Pro SP4, XP Pro SP3, Vista Ultimate, 7 Ultimate SP1, 8.1 and, for kicks, Linus Mint installed. Windows 98se is next... Why am I doing this? LOL! I'm not sure but I think I was bored one evening and decided to play a bit. When you are retired you can do just about what you want when you want.
Also, with my having almost 13 TB of disk storage, I don't really have to worry about using drive space. For me it is just sort of fun to play with this stuff.
Oh yes, I DID say there was going to be some useful info... This pertains to systems that are AMD based using a UEFI BIOS and using VirtualBox as your virtual machine manager. For what it is worth I highly recommend VirtualBox as a virtual machine manager.
There is an issue with some AMD based UEFI BIOS settings in relation to VirtualBox. To be able to get the best performance, and to be able to even be able to install a 64bit OS, AMD-V MUST be enabled in the BIOS. At least on my system there is no listing for AMD-V in the BIOS. Instead, for some reason that I cannot fathom, it is listed as 'SVM'. If you want to make full use of a virtual machine on an AMD based system this setting MUST be enabled.