The GIMP (GNU Image Manipulation Program)
Downloading the GIMP
The GIMP is a freely distributed piece of software consisting of the main image manipulation package and a library package available for developers and advanced users.
The Windows version can be downloaded from GIMP for Windows or an automated installer can be found at sourceforge.net.
I would recommend the automated installer for anyone not familiar with source code. Otherwise there is a good tutorial on compiling GIMP 2.3 for Windows at gimptalk.
You can also download the individual .zip packages for GTK+, GLib and other libraries at this GIMP download page.
Apple Mac and Unix platforms are also supported and can be found at the links below.
Loading the stable GIMP automated installer version 2.2
At the time of writing the GTK+ Runtime Environment was at version 2.10.6 (for Windows 2000 and newer) and the GIMP version was 2.2.13.
Firstly unzip the two above files.
If you have a previous version of GIMP loaded go to the GIMP menu and uninstall it.
Click on the GTK+ Runtime Environment executable (.exe) file and load this first on your system.
Now click on the GIMP 2.2 executable and load this to your system.
That's it, you should be up and running.
Loading the development GIMP automated installer version 2.3
At the time of writing the development automated installer GIMP version was 2.3.12. This installer file includes the GTK+ Runtime Environment version 2.10.6.
Firstly unzip the above file.
If you have a previous version of GIMP loaded go to the GIMP menu and uninstall it.
IMPORTANT: If you did have a previous development version of GIMP loaded, go to your C:\Documents and Settings\user\.gimp-2.3\ directory and find a configuration file called pluginrc. Delete this file.
The new version will create its own pluginrc file. I changed versions from 2.3.9 to 2.3.12 and GIMP kept crashing on startup, until I found a fix on a GIMP chat forum. I'm not sure if this is a bug in only the 2.3.12 version installer, but it will save you a lot of time and frustration.
Click on the GIMP 2.3 executable and load this to your system.
The developement version 2.3 should now be up and running. As its name implies, it is a development release, leading up to the official release of GIMP 2.4. Consequently it isn't as stable as the 2.2 version, but in my experience it's not that unstable and absolutely worth loading if only to check out some of the new features. Personally I much prefer the development version and can't wait for 2.4 to be finalised and released.
You may find it advantageous to save your project at regular intervals though, it will save the inevitable cursing/tears when it does lock up on you 
Script-Fu
On some of the tutorial pages we've added links to sites where you can download GIMP Script-Fu's. These are scripts or macros that will do the described tutorial automatically for you.
We have written and linked to a few Script-Fu's for some of the tutorials descibed. These can be accessed from the Script-Fu download page, we hope to add a script for each of the tutorials in the future.
To use the script you want, download it and then copy it into your .gimp-2.2/scripts directory. Do a search in your GIMP folder location for *.scm files if you have trouble locating the directory.
Next open the GIMP and on the main toolbar refresh the scripts by going to
Xtns » Script-Fu » Refresh ScriptsNow when you open the image you want to work on, you can find and apply the script by looking for it on the image toolbar.
All the Scrit-Fu's downloaded from here will be under
Script-Fu » Underwater PhotosThere are also GIMP 2.4 versions of the above scripts on the Script-Fu page, as the new script program has changed slightly meaning the old ones do not work in GIMP 2.4.
