On Tuesday, March 11, 2003, at 04:21 AM, Jack wrote: > Looking to add more RAM but don't know what I need. > Does my G4 Powerbook 550 mhz use PC133, PC2100 DDR or..... Ever been to www.crucial.com ? They have a walk-thru system that tells you *exactly* what memory you need. Just to be nice, I walked through it for you - go here: http://www.crucial.com/store/ listparts.asp?Mfr%2BProductline=Apple%2BPowerBook&mfr=Apple&cat=RAM&mode l=PowerBook+G4+550MHz&submit=Go