The HD503 is solid black with an aluminum front bezel. There is an LCD screen on the left side of the bezel with multiple buttons below the screen as well as a volume knob. On the right side of the bezel are two stealthed bays. The upper bay is designed to hold an optical drive while the bottom bay features a hot swap bay and front panel I/O connections (microphone, headphone, two USB 2.0 ports and an eSATA port). eSATA on the front is a nice feature that will go a long way when transferring large files to / from an external storage drive.
There are two vented slots on the left side of the chassis. The front vent supports a 120mm fan for cooling the hard drive(s), although one is not included. The passive vents near the rear are positioned to aid the power supply fan, depending on the type of PSU you are using.
On the back of the chassis we find a typical setup with the power supply at the "bottom" of the case. Two thumb screws hold the top panel in place and Zalman has even included a small handle to help remove the panel. I really like this simple feature as every other HTPC case I have worked with made it somewhat difficult to remove the top panel as there wasn't anywhere to grip the panel when moving.
The add-in card slot covers are vented and replaceable. Two 80mm fans are included in an exhaust configuration just above the CPU area.
On the right side of the case are two additional vents. The one near the CPU area supports a 120mm fan (not included). The vent closer to the front of the case is just a passive vent and you can't install a fan here due to the optical drive cage being in the way.
More just ahead.