Size

A 160 GB drive will likely be the the smallest one available on a new desktop computer or 80 GB for a laptop. Doubling that capacity may cost only a small percentage more. However, certain computer activities (e.g., editing digital video) may require much more drive space. If you use multimedia applications, you may need a larger size.

Rotational speed

Newer drives can transfer data fast enough for the most demanding tasks, including digital video. A hard drive rotational speed of 7,200 rpm is considered standard for a desktop computer (7,200 rpm for a laptop), and 15,000 is close to state-of-the-art. Drive performance is more complex than a single number can express, but most current drives are quite fast.