Wow, Are you using the machine as a server or for other purposes?
Why don't we make it a rule of thumb that if you don't how to configure it, pass it to me.
Yes you have to recompile the kernel. The options you want is under :
Processor type and features
-->Symmetric multi-processor support (X) processor -->replace X with number of processor on board.
-->High memory support -->4Gb
Make sure you DO NOT enable ACPI under Power Management Option.
Here is my experience with HighMem+ACPI: