Good to hear
After all, XP by itself cannot write anything to those disks, so it's normal that it shows 0 byte available. Burning programs are another matter.
As for the magnetic thing, CDs and DVDs are a high tech version of gramphone disks (read and written by laser, the etches on their surface are not visible, but it's still a spinning disk with etches in it like a gramophone's). They have to be stored like a good wine (dark, fresh, not too much moisture), but that's it.
Hard drives are the ones that use magnetic platters so can be damaged/erased by BIG magnetic fields.
A good thing you can do if someone helped you (other than posting "thanks a billion" which is always welcome for us volunteers), is clicking on the balance on the top right of the helpful post to approve it.