Windows XP can only use about 3.3GB.
Use Task Manger to kill off background processes and services that you
don't need for the moment.
Close all MapInfo Tool Manager utilities that are loaded.
That will free up some memory. The only other option is to keep an
older version of MIPro installed (if possible).
Then in October you can pick up the Windows 8 64-bit upgrade for
$US40. Can use all your 4GB of RAM.
Ross