Hi ltcjc1952,
The COA is the important part. Any disc that matches you COA (ie: Windows XP Home) should work to reinstall Windows for you. You just have to find the the disc that matches whether your Windows Release is an OEM or Retail Version. Your computer manufacturer will be glad to sell you the new media disc for usually around $60.00. However, if you can find a friend or associate that has a disc that matches your license you could borrow it and install with your Product Key from your COA.
Cheers!