The V64 I have uses custom memory designed for it...so you can't use pc memory. The cd64 I'm not sure if that uses pc memory, the z64 uses zip discs, not sure about memory type and the V64 junior is the only 512mb one out of the lot but needs batteries and is like a n64 cart.
http://en.wikipedia.org/wiki/Doctor_V64
http://www.geocities.com/Baja/3222/backup.htm
http://www.robwebb.clara.co.uk/backup/