Re: What do I need to Re-build my old computer.

In order to upgrade processors, you do need to replace the motherboard. 

With a PC as old as 1996, there is very little of the old PC that you can use - 
the newer motherboard will require a different type of memory, and also have a 
different mechanical shape (ATX), that will probably not fit the old case, as it 
has on-board serial/parallel ports etc. ATX motherboars also require an ATX type 
power supply, which your old PC almost certainly won't have. 

I think you will find it cheaper to either buy a complete new PC, or build one 
from modern parts. About the only things that you may be able to use from the 
old system are the monitor, floppy drive and possibly the CD-