Either use the help function of XP to look up how you can burn CDs or just simply drag&drop the files you want to burn on your CD-recorder drive in the Windows Explorer. XP will tell you what to do next. I'm not sure XP supports burning of DVDs natively.

About Nero. The reason why it takes system resources is probably some instant burn feature. A lot of burning programs offer to use CDs like "ancient" floppy disks. Maybe Nero has an option were you can turn that off.