Q:

VM Resolution can't go over 640x480, even after guest additions were installed

This is on VirtualBox, guest is Xubuntu 32bits 14.04, host is Windows 8.1 64bits
I should point my hardware does not allow x86 virtualization, hence why VirtualBox only allowed a 32bits VM to be installed. 
Side note : It's an AMD FX 6300, although in the specifications it says virtualization supported, my BIOS says otherwise.

A:

When your VM is shut down, change the available video memory to something higher.  (I use 128 MB - the max allowed)

