XP can not find 128mb SD when inserted?

I have a bunch of 128mb SD cards (actually other size cards too) that no longer work. They have worked in the past, but when I put them in a card reader and hook up to an XP computer, there is nothing there ... like I said: they DID work before. I don't really care, if I ever get the data back off of these cards, but I would like to use them, rather than just keep throwing them away, after a while, and buying new ones. I use them in several different digital cameras, and like I said "they DID work" before.

When I put them in the card reader now, and go to "my computer" and click on the reader, it just says "Insert Disk". I hit retry several times and get the same error. Any idea how to get these disc back to where I can use them again ?