A friend of mine has a Toshiba A135-S4527 laptop and wants to increase her memory; she only has 512MB. Did some checking online and determined she can install up to 2GB memory.

Can anyone tell me what the issue would be if she were to install one 2GB memory stick instead of two 1GB memory sticks? Someone told her she needs to use two sticks to max out the memory and can't use the 2GB stick.