Running Intel Xenon 5630, 80GB of RAM, 146GB 15K RPM Hard Drives. Multiplied by 6 blade servers. The rack mount also houses 6 power supplies for redundancies. Everything on the rack is hot swappable, including the fans.
The idea behind thin clients is that the desktop tower we are all use to is replaced by a monitor and a little box that connects to the server and loads the OS with all the apps from the server. You can think of it like a dumb terminal from the old days.
This makes it easier for the IT department to maintain and deploy applications from the server room. This is also more efficient with power and heat over the desktops not to mention it also saves a lot of space.
The server and clients run a special version of called Windows 7 for Embedded Systems.