Well, that board has the Via KT266a chipset, right? That only supports 266 FSB speed which is the PC2100 RAM you currently have... You may be able to tighten your memory timings some, but you really won't notice any real improvement with tighter timings.
You won't notice any difference at all going to 1 GB of RAM from your current 512.
Scout
700 Mflops in SETI!