This is all bad advice.
Compatibility mode is used to keep old, unmaintained software running. OTOH VirtualBox is actively developed and maintained. Plus the idea that it might be more compatible with that disaster known as Vista than with more recent Windows versions is frankly ludicrous. VirtualBox is cross platform, based on the Qt GUI. What on earth do you think it would require that only Vista provides?
Setting a compatibility mode will probably do nothing at all. At best it will hide the actual problem (probably a path or environment issue) and make it impossible for anyone to help you remotely.
With that I'm now going to lock this topic to hopefully stem the tide of future misinformation.