The BIOS does support V-x and it is enabled. However, the Intel U5400 does not. It is a 64bit proc running Windows 7 64-bit.
The Vbox user guide clearly says VT-x hardware support is not required but the BIOS MUST support 'enabling' of it:http://www.virtualbox.org/manual/ch10.html#hwvirt
As opposed to other virtualization software, for many usage scenarios, VirtualBox does not require hardware virtualization features to be present. Through sophisticated techniques, VirtualBox virtualizes many guest operating systems entirely in software. This means that you can run virtual machines even on older processors which do not support hardware virtualization.
Even though VirtualBox does not always require hardware virtualization, enabling it is required in the following scenarios:
Certain rare guest operating systems like OS/2 make use of very esoteric processor instructions that are not supported with our software virtualization. For virtual machines that are configured to contain such an operating system, hardware virtualization is enabled automatically.
VirtualBox's 64-bit guest support (added with version 2.0) and multiprocessing (SMP, added with version 3.0) both require hardware virtualization to be enabled. (This is not much of a limitation since the vast majority of today's 64-bit and multicore CPUs ship with hardware virtualization anyway; the exceptions to this rule are e.g. older Intel Celeron and AMD Opteron CPUs.)