I wanted to try Windows 8 on my new Ultrabook, but I didn’t want to mess up a perfectly good Windows 7 installation with a beta OS. And then it struck me: I can boot Windows 8 from a virtual hard disk. So can you, following these simple steps.

For the last six weeks, my portable PC of choice has been an ASUS Zenbook UX31E. It’s a wonderful little machine—light, fast, fun to use, and a great example of what’s right with the whole Ultrabook category.

I wanted to try Windows 8 on this machine, but I didn’t want to mess up a perfectly good Windows 7 installation. This is, after all, a machine I use for work, and Windows 8 is still a beta, with some rough edges.

The Zenbook has a 128GB SDD, which is fine for a secondary work PC but not enough to split in half for a conventional dual-boot setup. After a few milliseconds of thought, I rejected the idea of trying to shrink my existing disk partition so I could pull that off.

And then it struck me: Wait a minute. I can boot Windows 8 from a virtual hard disk on this machine!And 30 minutes later, that’s exactly what I was doing.

--> Please see the rest on the blog : http://www.zdnet.com/blog/bott/how-to-use-a-vhd-to-dual-boot-windows-8-on-a-windows-7-pc/4847