Even if you had to pull it...you could sell it (vice throwing it away) or perhaps put it into another machine.
If the system has a dual channel memory architechture...matching pairs of DIMMs gives best performance.
My mom's computer has two 256MB sticks of DDR2 memory. The crucial website says that the modules are best when paired. She only has the two slots, which means that getting more memory would mean buying it all new and throwing away the old. My question is, is it essential that the modules be paired up, or can they just be mixed? If they can be mixed will there be a large performance hit?