I know this is a really old topic, but i'm currently playing around with my old pr, an optiplex GX1 its runnin a p3 with 64mg of ram, pretty sure its a pc100 card. Just want to know if i shouls stay with the pc100 or will a pc133 work? Also if it will be ok to use a 256 card with the 64? I've heard that these comps support up to 384 or something. Any help would be great.