Bought a new memory stick to back up
I know this doesn't answer your question per-se but ....
Word from the wise.... the use of the words "back up" in conjunction with "memory stick" is something that should never, ever happen.
CDs,DVDs,External hard drives,DAT/DLT/LTO tape ... fine.... but memory sticks.... only if you've got a death wish... they are only (just about) fit for
ultra short-term storage.
Irrespective of storage medium, anything important should have multiple independent copies and preferably on different storage media / different manufacturers.