Do you mean an extra
1GB of RAM? If so, it depends on the requirements of the Operating System you have and the software you normally use.
The greatest improvement will occur if the system is currently running out of memory and utilizing the paging file on the hard drive. A process which does not provoke paging will not directly benefit from extra memory, as it doesn't need it. If you notice lagging performance and the hard drive is active at those times, extra memory will likely be very helpful. (Although a malware infection or a background virus scan can cause similar symptoms.)
A further potential benefit is if your OS is a later one that uses pre-fetch, more memory allows more potentially needed modules to be pre-loaded into memory, so this may further reduce delays due to hard drive access when those modules are called for.
If you simply plan to replace the existing 1GB of RAM with faster memory, it will depend if your motherboard supports the faster RAM. If it does, memory data transfer will be slightly faster, but it won't make a big difference to the overall performance so you'd notice it.
Edited by Platypus, 03 July 2009 - 07:12 AM.