The first is called ISO Recorder (referenced from this Microsoft article). It adds the ability to copy a CD to an ISO image (a file) on your hard drive. It's a very simple extension, and much more lightweight than installing something like Nero. There's a short tutorial that explains how to use it.
The next one is called Virtual CD-ROM Control Panel for Windows XP (referenced from this Microsoft Article). It allows you to "mount" an ISO image file and have Windows pretend it is a CD in a drive. I tried it on two ISO images. It mounted the one just fine, but locked up on the other one. I ended up installing & using Daemon Tools instead. It does the same thing, but is much larger & wants to install adware to help support the project, so be careful.
Finally, I had to reinstall the games from the ISO images so that the games knew to look at the "new drives" instead of the actual CD drive. There may be a way to update the configuration instead of reinstalling, but reinstalling from the ISO images is pretty fast anyway.
Hopefully somebody else will find this to be helpful.