Is your machine a Pentium III ?

The pentium IV's have moved on to be whole different animals.

You would not be able to use many of the parts on your old motherboard on your new motherboard.

a) Ram would be different and not usable.
b) Power supply would be different and larger on new one.
c) I could not tell you if your case would be usable for the new motherboard - many of the proprietary companies use proprietary motherboards.

It would almost be like buying an entirely new machine - which is probably better anyway.
You can use your present machine and network them together.