4GB SanDisk card not seen by Windows or Rescue Pro

I have a 4GB Compact Flash card that gets an error 99 in my Canon DSLR.  When I plug it into my card reader on my Windows 7 PC, it fails to detect the card. Rescue Pro doesn’t see the card either. I’ve tried formatting the card in my camera but it says it can’t be formatted. Is the card totally dead? Any other options to fix it?

sounds like a dead card. format fails and not detected are 2 symptoms of a failed card.