PC DOS may be far too old for this usage. I would fetch a dos boot disk of more recent vintage from http://www.bootdisk.com and use that as the boot A: source for this CDR.

http://www.bootdisk.com/nero.htm writes...

"And Here's Another Way For You To Make Bootable CD's

To Create A Bootable CD, You Need A CD-Burner, Roxio Easy CD Creator, A Blank CD-R Disk And The Bootable Source Media. (The source can be a floppy diskette, a hard drive or a previously created image file of any of these. Use "Help" if confused at step four below.)

After You Have Gathered Everything Together:

1. Put the blank CD in your drive
2. Start Easy CD Creator
3. Select "File", "New CD Project", "Bootable CD"
4. Select the bootable CD type
5. Then Select "OK"