So I bought a card reader that can read CF, XD cards, among other things. When I connect the card reader to the computer and insert my CF that I use for my 404, it asks me to format the card, or else it cannot read it. I obviously don't want to do that because I have some samples on there that I don't want to get rid of.

I tried getting a brand new CF. I insert the card SP404 and let it set up its folders and whatnot, but I get the same error when I connect to the computer. Will I have to get a different card reader in order to view the cards, or do you think that my compact flash cards are the problem?

Why wouldn't you just back up the files on your first card to a folder on your computer then format it in the 404 and re-copy the files from the folder onto the newly formatted card with you card reader and then load it into your 404.

or you just export the samples u have in the card as aif/wav files then formatting the card in the sp-404 and then copy 'em back.