You should transfer all of the save game directories to disk. If you can't fit them all on one disk, you can zip the directories or save all of the files individually.
On your computer the directories will be something like . . .
C:\Program Files\Black Isle\BGII - SoA\save
and
C:\Program Files\Black Isle\BGII - SoA\mpsave
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Most Subtle Official Straightman of the Laughing Hyenas -- Grammarian Brigade.