Looks like it stopped after migrate_files ( function in that script ) and now it refuses to do it again because it checks if partition is formatted - you can see part of script that checks it here
if mount -t auto "$dev" $target 2> /dev/null; then
if [ $(ls -1 $target | wc -l) -gt 1 ] || \
[ "$(ls -1 $target)" != "lost+found" ]; then
echo "Volume $dev is in use. Aborting"
umount $target || true
if it find folder lost+found, which is usually on ext filesystems, it prints out Volume is in use and exits.
and possible solution
So, if you still can boot into wubi, delete filesystem from that partition by running gparted, select partition /dev/sda7, delete it. Then make new unformatted partition on same spot ( right click on unallocated, new, choose filesystem unformatted ). And run script again
possible solution if script will stop again
if it will stop again after copying files from /var/tmp, check what is there and you can exclude it from copying by adding --exclude /var/tmp/folder_that_dont_like_to_be_copied
parameter to this part of script after --exclude=/sys/*
echo "Migrating files..."
rsync -av --exclude=/host --exclude=/mnt/* --exclude=/home/*/.gvfs --exclude=/media/*/* --exclude=/tmp/* --exclude=/proc/* --exclude=/sys/* / $target