Bootable ISO image

This thing just crossed my mind. Does anybody know if there is a program that could boot from a CD, load an ISO image from a disk and boot that image? The idea just popped up because I want to install windows, but I don't have any empty CDs any more (who has these days). I do have an USB disk that could fit the image, but my mainboard doesn't have boot-from-USB.

doesn't sound very possible. Closest thing I know of would be PXE network boot.