Migrating to new user account: must chown old account's files... I think
You can check and re-assign ownership recursively over a directory tree with find, stat and chown.

#!/bin/bash

olduser=&lt;oldusername&gt; # replace this with your old username
newuser=&lt;newusername&gt; # replace this with your new username
dir=&lt;dir&gt; # replace this with the directory you want to run through

find $dir | while read filename
do
  owner=$(stat "$filename" | cut -d ' ' -f 5)
  if [ $owner == $olduser ]
  then
    chown $newuser $filename
  fi
done