What EyeForOne said. Plus, there are limitations on whether or not the board will support high-density chips (early in SDRAM history low-density chips were mounted on high boards - PITA). If it's a manufactured PC (HP, PB, Compaq, etc) then there will almost certainly be a lowered maximum number that is BIOS limited. In that case, you might want to save up for a new machine. If you reuse your hard drive, video card (if possible), optical drives and floppy you could build a new box for less than $200USD shipped.