Importing Guitar Hero™ songs
The game has a built-in importer for the songs in Guitar Hero™ I and II by RedOctane. To use it, you'll need to have the game DVD, at least 500 megabytes of free disk space and a lot of patience.
You'll also need to have the OGG Vorbis command line compressor installed. In Linux, you can usually get it in a package called vorbis-tools. In Windows, copy the encoder (oggenc.exe) into the game directory.
The importer can be started by choosing Song Editor in the main menu, followed by "Import Guitar Hero(tm) Songs". The importer will ask you the path to where the game files can be found. Usually this is just the driver letter of your DVD drive, e.g. 'D:'.
After you have entered the correct path, the importer will start ripping the songs. Note that this will take a very long time. For example, on a 1.8 GHz Pentium M laptop with 2 gigabytes of RAM the process took about 4 hours. It is recommended that you run the game in windowed mode so that you can leave the importer running in the background and do other things while it's doing its magic.
Once the importer is finished, you'll find the songs in the regular song selector. Note that if you abort the importer midway, it will mostly pick up where it left off when you run it again.