Does PC133 SDRam Really Make Difference?

I recently assembled a computer and I cannot get it to work right. My speculation is that I have PC100 SDRam in there right now and it requires PC133 SDRam. Can anyone tell me if the two really make a difference? The Motherboard (Abit KT7A Raid) Says to use PC133 but I wanted to try the PC100 since that is what I already had. Should this change make a significant difference?