You will need a new power supply as your older MB will be an AT and newer are ATX. Additionally, the power switch used with the older power supply will not work. Newer ATX supplies are momentary operation while older ones are on/off. Next, your P4 will generate more heat and your case will need to offer good air movement. Additionally, your 440 has ISA MB card slots mixed with older PCI slots and a new MB will have PCI only plus one AGP for video. You will not be able to reuse any ISA cards such as modems, etc. While you might be able to reuse your old case, it may not be a small and inexpensive project.