Most products like to say in the instructions "Install drivers first, then plug in the device", but I love to throw caution to the wind; the moment it came out of the box it was plugged into a USB slot faster than you can say "Microsoft-HID-compliant-device".
It was recognised instantly in Vista as a USB keyboard. Most of the standard features work without the need for the Logitech software, but then again, you might as well buy a cheap keyboard if you wanted just that.
Thankfully, putting in the CD and installing the software was painless. The drivers restart the keyboard, and this time the LCD scrolls through several default installed programs. JOY!
By default, the G15 has a range of LCD applications pre-installed; some are specific to games, however, and will not load until the game itself is active. There are a number of 3rd party applications for the LCD that can be downloaded from the interweb to add greater functionality to the display.
Further to this, Logitech have given us the power to create our own applications by including an SDK with their software. For those who don't know, an SDK means you can make your own programs for the company's hardware, but unless you are a coder, you might want to forget this titbit of information. To make an LCD program for this keyboard you will need some proficiency in C++ and compiling said code with the supplied libraries.