Buying the right memory for your used laptop can be a little tricky, especially if you have an older laptop computer. This is a short guide to help you determine what kind memory your notebook requires.

There are big performance benefits from installing more memory into a notebook. Windows XP is a huge memory hog and to be honest it will really require a minimum of 256Mb. Since notebooks have slow hard disk drives when memory information has to be stored on the hard disk because all the memory is full your system will pretty much grind to a halt.

More memory allows you to explore your hard disk faster, have more browser windows open and edit pictures from your digital camera with ease.

What memory does your notebook take?

The easiest way to determine this is to use your CPU or processor as a guide. All Pentium II and Pentium III notebooks use PC 100/66 SD SODIMMs. Pentium IIs use PC 66 low density SD SODIMMS while Pentium IIIs use PC 100 SD SODIMMS. Pentium 4 notebooks use DDR SO DIMMs like the one pictured below.

Here’s a good example of a used laptop memory chip, all laptop memory types look similar. You’ll have to read the sticker to be certain you have the right kind.

What size can you install?

Pentium II notebooks have a limit of 256 (total memory 128Mb in each slot), while Pentium IIIs can take 512. Any Pentium 4 notebooks can take at least 1gb, perhaps 2gb.

All notebooks that I’ve come across have had 2 memory slots on the bottom of the laptop. Normally you just have to unscrew a cover and push the new memory in sideways then click it down flat into the spare slot.

If you’re after the technical details on actually installing laptop memory, have a look at our laptop memory upgrade guide.