I'm using a temporary Windows VM for testing upgrade image files, since I'm not aware of a Linux tool for e.g. applying builder images. I know how to simply reflash the kernel, but AFAIK builder images require the Windows tools - I'd love to hear otherwise!

KVM differs from VMWare in that it's stock Linux without needing to installing any third party software - VMWare isn't free either. The Player is free, but not the tools needed to make an image.

Jon.