Welcome to the space station Z820. Here you will find green-labeled access handles for all of your upgrade and maintenance needs:

Power supply unit

CPU fan assembly

Optical drive release lever

Lower case shroud

Hard drive release catches

Stowed away on the bottom we find clear evidence that this is no ordinary unit: this computer is "Property of Hewlett Packard Company," comes with a return address, and has some labeled specs that didn't quite line up with what's inside. (More on that soon!)