OK, the PC100 or PC133 RAM *may* work, or it may not.
It has to be low density if it is 512 mb modules (16 chip) or 256 Mb (8 chip), if it is PC133 it has to be dual-programmed to run at PC100, and the SPD settings have to be written correctly. How can you tell? You can't without trial and error.
Good USA RAM vendors for older Mac RAM are most frequently recommended here on MR; OWC (MacSales) and Data Memory Systems
Thanks
Trevor
CanadaRAM.com