What do people mean by "rack configuration"? How do I find mine? WHat do I look for?

the rack is the shelving system that rack mount servers sit in versus tower cases. I assume this is what you are asking about?

It's pretty much what it sounds like: Instead of having your computer in a case w/external discrete components (UPS, external drive(s), etc.) you mount these in a rack - an open-faced electronics cabinet with trays for each major assembly. the computer motherboard and adapters go in tray 1, the hard drives mount to tray 2, the UPS to tray 3, a tape backup drive to tray 4, a network router in tray 5, etc. Whatever components you need to complete your server assembly. They're used mostly for network servers or test and control stations: Where you need ready access to all major assemblies w/o going through the hassle of removing the case and fiddling around inside to get at the individual units. You can add racks to a rack assembly or even link separate rack assemblies depending on the complexity of the computer control system you're building. Rack configuration is an important component of Configuration Management when you're deploying testing stations to multiple sites; fer example smog test machines to different service stations. You want a car tested at any two smog stations to test to the same result and you want to know what parts you have to order when a smog station anywhere in your network breaks down.

Of course, in a broader sense, it also applies to your girlfriend's measurements... >;)

ROFLMAO Orion! Umm...I'm not sure what you meant by "tray 1, tray 2 etc" but as a rule of thumb when rack mounting, you always want the heaviest items at the very bottom of the rack. For instance, in the 30+ racks in the main server room at my workplace the UPS is always mounted at the very bottom. Then the servers above it (still as low as possible) with the lightest units (ie: router/wiring panel etc) at the top. A top heavy rack is a bad idea, if you ever slide the top unit out, the rack falls on your head!

heres an example of a rack mounted server: http://www.apple.com/xserve

my racks are mounted to ceiling and wall. No falling over racks in case of earthquake. Nor do I have to care about weight distribution.