Is the CD you have the full XP CD? If so, you can download SP1 or SP1a and "slipstream" it into your present CD to create an XP CD that has SP1(a) already incorporated into the installation. This has the added advantages that there are no backup files stored on your system (they are then on the CD) and a repair installation will already have SP1(a) included.
Create A Bootable Windows XP Installation CD Slipstreamed with SP1
Creating a bootable Windows XP SP1 CD
How to Slipstream an XP SP1 CD
Create A Bootable Windows XP Installation CD Slipstreamed with SP1
Creating a bootable Windows XP SP1 CD
How to Slipstream an XP SP1 CD