Every application that runs on your system needs to reside in RAM and when you run out of space the system will use your hard drive as virtual RAM and since memory is many times faster at transfering data than a hard drive it is highly recommended to have plenty of memory. Just how much memory you will need depends on the applications you use and how many you run at any given time but for general usage 512 MB should be sufficient. However, when you consider that memory requirements are always increasing and that the cost of memory is relatively inexpensive it would be wise to invest in an upgrade to increase system performance.

Apart from the amount of memory you install you should also consider its type. Older memory modules (e.g. PC100 and PC133) have been superceeded by new Double Data Rate memory with types PC2100, PC2700, PC3200, PC4200 and even faster DDR2 and DDR3 modules.

IMPORTANT In order to take advantage of Dual Channel DDR to double the speed of your RAM, memory modules must be installed in identical pairs (e.g. 2×512 MB or 4×512 MB).