I have a Performa 638CD, which is nearly identical. The problems I have with my machine are:

1. THE NOISE-The fan is quite loud, and it's position at the top of the case does not help matters at all.

2. FAN POSITION-The fan being located at the top of the case presents two obvious problems:

a. The vent is too easy to accidentally obstruct with the base of a monitor.

b. Once again, the noise.