Do I need to have the correct mhz (133mhz) or is this irrelivant. I only re-ask this as some think it is and others say it's not… also is the number of pins nothing to with it?

Answer:
What you need to look at is the speed of the memory either given in Mhz or pcxxxx. The other that matters is the max capacity the motherboard can handle and the type of RAM. You need to see if it is SRAM, SDRAM, or DDR (v1, 2, or 3?) Once you know all three of these, then go ahead and max out. The owners manual for the motherboard should tell you the maximum speed of the memory, type, and max capacity. If it is a manufactured personal, it might not say, just Google the personal or find out what motherboard was used and Google that.
Answer:
http://www.crucial.com/