The developer of SiriProxy, @plamoni, made a video on how to install SiriProxy on Ubuntu 11.10. If you don’t have Ubuntu, you can easily create a virtual machine on your PC or Mac with VirtualBox.

Set up Ubuntu on a Mac
Set up Ubuntu on Windows

If you successfully set up Ubuntu, you can start installing SiriProxy
Download SiriProxy Manual

Info: If you read iPhone 4s Key, you can setup a Virtual Server to get Siri work for iPhone 3Gs and iPhone 4 on the way.