I rebooted my machine at work and had a quick browse through the BIOS settings looking for ways to optimize the disk. Whilst changing those settings I spotted another called Hardware Virtualization. Turns out that most modern processors from AMD and Intel support a special set of instructions that allow virtual machine software to bypass parts of the emulated layer and go straight to the processor. However, for Intel processors these are typically off by default. So if you use application like Virtual PC then turn this on in both your BIOS and the VPC settings and enjoy a small, but real, performance boost.