I have a toshiba laptop(checked with crucial .com already)
currently it has 2 memory sticks...one is 2700 and one is 2100
it takes 2700 but supposedly its backward compatible.
both are 256..I wanted to upgrade so I purchased a 1 gb that is 2100...bu when I place one in with either one of the other memory sticks my computer does not turn on/??? the 2100 thats only 256 works with the other memory stick...should I use the one gb bu itself or is their another issue /?? so confused
sorry for the dumb question

I will asume your laptop is new enough to contain dual channel RAM, dual channel RAM should ONLY work with two or four (or more, but its not recommended and wont fit in a laptop) sticks of identical RAM.

Your laptop will probably work with the single 1gb stick, but will not function with 256mb sticks.

BTW what do you mean by 2700 and 2100? RAM speed??

I believe the laptop came out in 2004 that's when the original owners bought it new.
I'll get the model number when I am at home but I looked it up on crucial.com and it said it should support
dual Chanel ram .I opened and it has two sticks currently one says 2700 the other 2100 (256 mb)
I figure if one says 2100 which is also what the 1gig says that it should work.
I have only tried using the 1 gig with each of the 256 sticks never alone..do you think its possible just by itself without the other two.
It said my system should support up to 2gig.

here is the update
although the two sticks that were in the laptop were different ..and worked together
neither worked with the 1 gig..but I tried the 1 gig by itself and it works!
laptop is toshiba a50
on crucial.com it says I don't have to instal matching pairs because it supports dual channel memory configartion....