Hello Traymond61 Yes, that configuration will work.  You can populate 2x2GB DIMM's in 1A and 1B and not populate DIMM's in any other slots.  Here is a link to the installation guide on the PE1800.  If you look under the system memory section it lists the memory population rules for the server.  <ADMIN NOTE: Broken link has been removed from this post by Dell> Thanks
I have been getting some blue screen memory parity errors on my Poweredge 1800 .  Hardware log reported a problem with  Bank 2.  I am currently running 4 gigs of ram.  2x1gig in bank1       2x1gig bank2.  I swapped the memory modules to see if the errors follow the memory modules or if i have a problem with bank2 on the Motheboard. Question. If it does end up being a problem with the memory slot on the MB  could i just put  2 x 2gig modules in Bank 1  and take Bank2 out of operation and this would solve the problem.  I don't  want to replace the MB if i can get around it.   Thanks
Bad Memory Slot / Bank