Navigate to the System Update (X) drive, and create 2 folders, one labeled "A" and one "B"

Extract all of the files from OSU1, and copy everything in $SystemUpdate, except for "updater.xvd"

Paste these files in the folders "A" and "B" that you created.

Copy "updater.xvd" from $SystemUpdate and paste it in the root of System Update (X)