From AiboStuff, the free AIBO community wiki
A Memory Stick is a flash memory card produced by Sony and is used in all models of AIBO to contain the personality, Photographs taken by the AIBO, settings and other relevant data. Most AIBO Memory Sticks are relevant only to the software which they contain and are protected by encryption written to the stick during its manufacture. Aside from the commercially available personality software, PMS sticks were also produced in order to allow users to write their own software for the AIBO platform or try 3rd party examples available through the community. Again, the PMS sticks contained encryption preventing the use of standard Memory Sticks in all of the AIBO model range except for the ERS110? and ERS111? models which permitted use of non-encrypted sticks.
Following the discontinuation of AIBO, a community written program called Stikzap was made available prodiding the ability to backup the encryption held on the Memory Stick. This allows successful repair of corrupted commercial personality and PMS sticks.
Due to the encryption data on the stick, Memory Sticks should never be formatted as this can erase the encryption turning it into a plain blank stick unusable in the AIBO . It it worth noting that the use of non-Sony memory stick readers can cause corruption to AIBO memory sticks, therefore it is strongly advised that the use of original Sony equipment be used at all times. Suitable card readers are available in the form of Sony USB stick writers, the Sony Clie Palm based organiser, Sony computers with built in card readers (Such as the VAIO series) and Sony digital cameras.
The lifetime of a memory stick is currently unknown, but it is proven that the lifetime of flash memory decreases with each write action.