OK - Maybe scrap the whole thing you've burnt to a CD and burn your .iso to a Virtual CD?
Virtual CD - The Original Then boot that and you can install.
edit: just seen its PC only... hang on let me see if i can find anything
edit2: Just done some googleing and found this:
Try and mount your iso into a Virtual Disk using Disk Utility.
edit3: done some further reading and found an easier way.
Right click the iso, select Open With -> Disk Utility
When Disk Utility opens, you can see the ISO in the left pane where the mounted drives are. You can either mount the ISO as a virtual file system or burn a CD.
You want to mount the iso