Apart from the Mac OS X EULA not allowing virtualization (only for Mac OS X Server and that only on a Mac) VirtualBox does not support Mac OS X / Server as a guest system. The only way to make this work (technically) is to do a Hackintosh install within VirtualBox which I cannot really recommend. You'd be using several pieces of software that were explicitly not meant to be used together. You experience of Mac OS X would be nowhere near the real thing.
Don't know about VPC, I stay away from MS products, but the totally b0rked way of a Hackintosh install might be feasable, but is likewise not recommended.