My brother needs a memory upgrade from 64 to 128 MB. Is it likely that a later model Pentium 2 or an early Pentium 3 vintage PC from the late 90's would use PC-100 SDRAM? I'm not holding anyone to it, I'm asking if this is the most likely. Thank you.

Yes, you are correct. It will most likely use PC100 SDRAM. Check crucial.com to be sure exactly what kind he needs and how much his motherboard will support.

If you can get hold of the mobo manual and take it to a good computer spares provider it would be well worthwhile. If you try to save money it may end up costing more. I have read many times on websites that 130 will slow down and run fine on a 100 machine but mine wouldn't have it. I then got a good quality Kingston 100 memory stick, carefully selected by the supplier against my mobo, and it worked fine. Derek

Go to either Crucial or Kingston and use their memory configurator to get exactly what you need. Both have great RAM, Warranties and a thing called service. Crucial will ship your RAM to your door(free) in two days or less. I got 128RAM for my Dell XPS Pentium Pro, cost $86(US) from Crucial, Dell wanted $1100 Canadian. It was at my door in two days from Idaho to Canada, that is service! This was a few years ago.