I downloaded a disk image used for a wargame hosted by stripe, but I cant figure out how to create a virtual machine from this image. I'm using virtualbox, but I could use another tool if it would be easier
Burn the image to a dvd or mount the img, and then boot from it.
You can now install it into a VirtualBox VM. Follow the steps in the link below.
Make sure "Mount CD/DVD Drive" is checked. If you're going to install your virtual system from a boot CD or DVD, put it in your computer's drive, then select "Host CD/DVD Drive." If you're using a downloaded or custom-made ISO file, select "ISO Image file," hit the folder icon to the right of the drop-down box, and then hit the "Add" button and browse for the ISO you're using. Once you've added an ISO file to this menu, you can mount it in any virtual machine you're running at any time
Ive used IMGtoISO and have been pleased with it. Its free and easy to use. Plus the ISO format is more compatible with more applications.