Just wanted to add some good information on using Virtual Box to install Windows 7 or Windows 8 (see my post here about installing Windows 8 into a virtual machine using Virtual Box.) Or any other OS for that matter. For more information about using Virtualization check out this post.
OK so the fix for the issue.
While installing Windows 8 (or 7) or other Operating System you may run into the issue where you are booting from a virtual or real CD/DVD and during the installation process it just ‘hangs’ at the ‘Expanding files…’ part of the install at the beginning. It will usually get to somewhere around 98%-99% and just hang there. Very aggravating. The solution is really simple!
Shut down the machine. Then On the settings tab, go to storage and then under SATA Controller you’ll see you virtual hard drive. Remove that using the button remove attachment. Then on the IDE Controller there is a small button “Add Hard drive” click that and locate you virtual hard drive you created earlier.
By doing this your hard drive will come under the IDE Controller. This fix worked for me on a Windows 8 and Windows 7 installation, I kept getting stuck on expanding files but this worked. No fuss no muss and all installed and worked well and very fast!
I hope this helps some.