3-4GB
The default a year ago is giving way to double this capacity. If you're heavy into graphics and games, this could seem small rather quickly. It should be fine for a casual user, though. Read about Alsoft Products to find ways to get the most out of the drive.

6-10GB
The current default. Well suited for most general uses.

13GB and above
Media professionals' hard drives can fill up fast, so consider your intentions for your computer realistically.