Looking at pie charts suggests you are looking at My Computer and at
the space available for storage on Hard disk. This is NOT to be
confused with Memory (virtual or not) which is the few hundred MB of
random access memory that programs run from, together with overflow in
page file.
If you are seeing 'low on disk space then you can turn off the warning
using the TweakUI power toy; but it sounds as if you are getting Virtual
memory warnings. See the Problems section at my page www.aumha.org/win5/a/xpvm.htm - this sounds likely to be the one
associated with Intel Application Accelerator, or possibly with Live
Update in Norton products