Your system apparently is not recognizing the new memory.
What system do you have? What are the memory requirements and limitations for the system? What are the brands, model numbers, and timings of the two memories?
Also could be a voltage issue - do you know what the required voltage is for the old and new memories?
Did you put the old memory back in and did it work properly?
Do you have multiplte memory slots and did you try the new memory in the other slot(s)?
I have a Dell dimension 2350, memory requirement is 512 for xp, have 2 ticks of crucial pc 2700 ddr, limitation for mother board according to Dell is 1gb,2.5 voltage on both. old memory works fine,i just wanted alittle more out of it for speed.just found out from Dell support original memory was pc2100ddr. was a hand me down from a friend because my hp got fried by lightning.
The bad news is that the specs say the maximum memory per slot is 512mb so it might be impossible to run a 1 gb stick.
The good news is that Dell offers a 512mb stick of pc 3200 memory as replacement memory for the 2350 so you may be able to go for faster 512mb memory. However at $29 a stick, $58 is quite a bit to invest for a modest speed improvement in a computer that age.
In a Dell computer, you have to be very careful in matching memory if you don't buy from them as they don't provide - or at least I am not aware of - a list of compatible memory. They want you to purchase from them. So if you are not matching the make and model already in the machine with just a larger size within spec, you might have a problem. Variables that can affect compatibility include, size, speed, memory timings, and voltage.
The specs only list the pc2100 memory speed, so at pc2700 you are already pushing it over spec - but this should not be an issue since they list the pc3200 for replacement.
The only other thing I could suggest is searching on the Dell forum or other web forums to see if someone else has already done a successful upgrade with different memory - of course you would still neeed to purchase it.
Its a backup til i can do better, once i can get on my feet ill give this one to a military family, thats a hobby of mine , i find pc"s on the side of the road and try to fix them for kids that mom or dad is overseas and cant afford a computer. then i give it to them 35 so far. its nice to have a parent say thanks when the child can do better in school cuz of a computer that some one didnt want anymore. thanks for the help!