The PS2 Save Builder is needed for when you're transferring files FROM your PS2 Max Drive TO your PC because for whatever reason, the files gets screwed up when you transfer the file from your PS2 memory card to the Max Drive.
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Download those two files from whereever you downloaded them from onto your desktop. Put the Max Drive into your PC's USB port. It should automatically pop up. With that window open, copy and paste the files into that window. The Max Drive will also appear as an "E" Drive if you were to go into "My Computer".
After copying and pasting the files, close the window. Now, eject the Max Drive from your PC and insert it into the USB slot on your PS2. Insert the AR disc and go to Memory Manager.
Find the files and copy them over to your PS2 memory card. DO NOT uncrush them yet.
With both files now on your PS2 memory card, uncrush/copy them from your memory card to your memory card. You should now have four files on your memory card. Two crushed and two uncrushed. Delete the two crushed files.
Remove the AR disc and insert 2K5. Both files should be listed and load without any problems.
Hope this helps.