ACAD 2007 Question

We've just recently upgraded from ACAD 2005 to ACAD 2007. I use ACAD
for manufacturing design and plant layouts. When working with a fairly
large layout drawing of a plant that is around 2,000,000 square feet in
size. There are a lot of machines drawn in the layout and when trying
to zoom, pan or just move an object the PC just drags and hangs up, it
appears that the drawing is maybe regenerating a lot?
I went under "Options" then the "Selection" tab, for "Selection
Preview" I unchecked "When no command is active", and on the same tab
under "Visual Effect Settings" I'm selecting only "Dash" in stead of
both. This helped a little but I'm sure there must be some settings
that allow a large drawing to be smoother and more manageable. The PC
is actually a laptop, an IBM Thinkpad T42P with 1Gb of RAM. Should be
plenty to run ACAD.
Any suggestions as to what other settings that are in ACAD 2007 that
will help?
Thanks,
Brian