how do I create a system backup disk
Do you have XP Home or XP Pro?
Assuming "system backup" disk means creating a full system backup:
XP Pro includes ASR - automatic system recovery. This tool creates a floppy
plus an image file that can be used to completely restore the system.
Whether you're using Home or Pro, I much prefer third party solutions and
specifically True Image from Acronis. A bit of a learning curve as there is
with all software but for the most part it makes it very easy to create,
maintain and use system backups.
NOTE: If you mean something else by system backup disk, you'll need to
rephrase your question and post again.