Random-access memory (usually known by its acronym, RAM) is a form of computer data storage.

What's the purpose?

Memory stores some of your operating system and application data while it is being run. The more memory you have in your system, the more application you can run simultaneously and will provide an overall better system performance.

What one should i get?

There are a few things you need to look at before purchasing RAM. Memory comes in many forms. Most of your older systems use DDR or SDRAM, while the current systems use DDR2 or DDR3 SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory). Make sure you check what your motherboard supports when buying RAM.

Software

It may seem strange but software should be a crucial part when choosing RAM. If you are running an OS that is 32 bit for ex "Windows XP Home", your computer will not recognize more then 3 GBs or RAM. So make sure if you plan on exceeding 3gbs of ram you have a 64 bit OS, for ex "Windows XP Professional X64"

Memory/Ram Checklist

1. However DDR2-800 memory will run the CPU bus at the optimal speed while slower memory are backward compatible.

2. It is recommended that you get the highest memory speed your motherboard supports if you want the maximum performance.

3. If you are on a budget then slower speed memory should be sufficient.

4. It is also best to get both pairs of memory from the same manufacturer to avoid incompatibility.

5. If you have the latest Intel i7 motherboard then you will need a triple-channel DDR3 1600, 1333, or 1066.

6. DDR-2 memory must be run in pairs to run at double data rate.