I have two sticks of PC-133 512MB RAM. There is only ONE machine I have gotten them to work on, and it was a crappy AMD Duron. Every other machine (Mac/PC) that I have put it in, it seems to want to bitch about. The memory is good, it's just that crappy of memory. I probably should throw it out, but I have the feeling I will get an off-chance to use it one day. I might try it in a Pentium III Board I have. It has a 133Mhz FSB, maybe it will work