Free Memory

Hi all,
I am helping my mother with her PC. Everything was fine until a few weeks
ago. She received an error message while initiating Outlook Express. It
would just hang and when she would exit from the program, she would get an
error message stating there is not enough free memory to run this program.
She currently has 128 megs and really only uses the PC for email and web
surfing. It is a Celeron and is running on Win ME 4.90.3000. If she does
not open OE, the memory message does not appear. I have removed OE and
reinstalled it but still no luck. It does not even retrieve her email. I
have used a virus scan and also scanned it for spyware/scumware. It appears
to be clean.
Any suggestions? It all began with OE not connecting.
Many thanks,
Faith