what memory to use

what is the difference between sdram 133 and pc2100 and whatcan run on my rig.xp 1500 k7t turbo 2 -fsb 145-sdram 100
all other settings are at default.this is my frist time in this forum.
hope this is not a stupid ?

Yes they are different, for one thing a older sdram stick will have two notches in it and two matching raised areas in the memory slot where ddr will have only one.
Also the pins or contacts are 168 on sdram and 184 on ddr(pc2100).

If you are not sure what to use go to www.crucial.com and use the memory selector for motherboards.

Welcome to the forums.

I'm assuming you have the MSI K7T Turbo 2. It takes PC-133 Memory. I would recommend Crucial PC133 www.crucial.com It can hit 150-160 FSB. There's a link you can follow that gives overclockers.com readers an additional discount. Anyone know where that link is? Hope this helps.