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To play any of the multimedia Mystery House games with a ".blb" file extension, you will need a Glulx interpreter -- basically, a "player" for files in the Blorb format. Since today's major operating systems do not have Glulxe interpreters installed by default (you can write to Bill Gates, Steve Jobs, and Linus Torvalds to express your dismay about this) you'll need to download and install one yourself. The process is slightly more involved than is visiting a Web page, but it's relatively painless and quite worthwhile. You'll be able to play IF without a network connection after you've set up an interpreter, and will be ready to use the Mystery House Taken Over Occupation Kit to create your own modified game, if you like.
You can find a recommended Glulx interpreter for your platform on the IFWiki. There are interpreters available for Windows, OS X, Linux, and other platforms as well.
Thanks to Java Web Start, and thanks to the developer of Zag, Jon Alfred Zeppieri, who set up the Mystery House Take Over games for use with his Java Glulx interpreter online, you can play Glulxe games online if you have a recent version of Java (1.4+) installed.
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