Not sure what you are getting at. Having a batch program run at startup does not constitute having made a OS. If you want to get into that kind of work even as a hobby, you have some learning to do. I'd suggest learning to using linux if you haven't already, and then learn to install a advanced linux OS like Gentoo, Arch or Slackware. From there, you can check out LFS (linux from scratch) or go into a custom OS build, which is what I do.
I start out with a net install of debian, installing only the minimum packages needed to run, and from there customizing it to how I like. When I'm done, I use the live-cd package to burn it so it can run off a disk, as well as install to HDD.
If you want to just have a batch file run off a cd, that's a different story completely.
