SP3 is just a windows update.you will need a windows XP install disk. depending on the version of it then it may already have SP3 on it. if not then windows update will download and install it
this is if windows update still works in an OS as old as XP though
My bad. If you can't boot by CD ROM, I assume you can boot by 3 1/2" floppy. All you need is a 3 1/2" floppy drive, a diskette and to down load the Windows XP boot disk program from the link above (I edited the post for XP). These boot disks load the CD-ROM drivers so you can install from the CD-ROM.lol where in this post was windows 95 mentioned