Sorry but the details are missing.
Reading http://support.dell.com/support/edocs/systems/opgx280/en/ug/specs02.htm I see one of the GX280's does not exceed 2GB.
There's also more to that 32 bit OS limit. Not only do you see 2.0 to 3.5GB ram being used, each process is limited to 2.0GB.
If you can get 2.0GB, button it up and move on.