Finding the Game
All of the games in the series are available in the King's Quest Collection boxed set. There are two versions: the original version released in 1997, and a Windows XP-compatible version released in 2006. The Windows XP version doesn't update the games to be XP-compatible, though: it just includes DOSBox to run the games (see below for more information on DOSBox).
If you're only interested in King's Quest VI and not any of the other games, you should look on Amazon, eBay, or other Web auction sites to find an original copy of the game. If you don't mind also picking up KQ4-5 along with it, you can find it for digital download at GOG.com. This collection has been updated to work properly with modern systems.
Of course, you could always download the game illegally from BitTorrent or other sites, but this walkthrough will not give any information on how to do that.
Running the Game
King's Quest VI was originally designed to run under the DOS and Windows 3.x operating systems. Therefore, running it on modern Windows machines can be difficult. With a little work, though, you should be able to get the game up and running.
This section will primarily focus on running the PC version of the game.
The recommended way to run the game, particularly the disk-based version, is to use DOSBox.
Running Natively Under Windows
If you have the CD version of the game, that version was designed to run under Windows 3.1, and will still run on 32-bit versions of Windows (64-bit users will need to use a DOS version in DOSBox). The instructions on SierraHelp's web site may be useful here. If you create a shortcut for King's Quest VI, you will need to modify its properties by right-clicking on it and selecting Properties. From there, go to the Compatibility tab, and choose to run in Windows 95 compatibility mode. Also, check the boxes to make the application run in 256-color mode at 640x480 resolution.