How Much RAM Do You Really Need?
(Excerpts from TomsHardware.com)

The bottom line is that there is not just one single answer to the question of how much system memory you need. However, to help you decide for yourself, we put together the following criteria:

512 MB There are a few situations where having just 512 MB system memory in your computer can be enough.

• If you run your games at low quality settings (small texture size) because you have an outdated CPU and graphics card, or because you prefer FPS over visual quality.
• If you only use one application at a time.
• If it is your grandmother's computer.
• If you are buying a new computer, even if it's a laptop, opt for more than 512 MB - you will never regret it.

1 GB Indeed, 1 GB of system memory will most likely be enough for the average user and for people.

• It will allow you to play new games at their highest quality settings, given that you have an adequate processor and a powerful graphics solution.
• You won't have to shut down non-critical applications when you want to play a game.
• You can (accidentally) press the Windows button while in a game without dying from a stroke during the seconds it takes to read Windows back into system memory from the swap file.
• If you go from 512 MB to 1 GB, you will notice the difference all the time. Starting up Photoshop while working with Word, an Internet browser, e-mail client and Acrobat Reader will go so much faster, and switching between the applications is a breeze.

2 GB Still there are situations where more than 1 GB is what you want.

• If you are a professional user, you might need more than 1 GB for really heavy applications.
• If you intend to do heavy multitasking, especially if you have more than one CPU or CPU core. Running RAM intensive games such as World of Warcraft, downloading files via high speed FTP or encrypted protocols, Bittorrent or any P2P program; decompressing large archives and playing large size video files in a window or on second monitor all at the same time can max out your system memory pretty fast - if your CPU can handle it.