BGInfo

BGInfo is a Sysinternals tool to display various bits of system information directly on your desktop.

It's especially useful if you often work with several computers simultaneously, since it allows you to check certain details about the computer's setup at a glance, as well as aspects of both hardware and software.

It has a small text processor that lets you edit the information displayed, like eliminating fields that you don't want to show and adding new ones from the list of available fields.

BGInfo also lets you choose the position of the information and whether it's affected by the screensaver.