Win2ksp4, Office2k pro updated

Using Excel when I attempt to open a second workbook I receive various 'out
of memory' 'unable to update display' err msgs.
The MS kb appears to suggest that the amount of memory available to a
workbook was increased in O2002 and again in O2003 am I reading this
correctly and therefore upgrading might sort the problem, or is there
another cause?

BTW I'm not using an HP printer listed on the MS kb, which apparently can
cause similar err.msgs

thanks