Adrian, You do this by removing the cameras internal IR filter...
When people mod their cameras for Astro use, they usually do this by removing the standard IR filter, and replacing it with a less aggressive IR filter by Hutech or Baader etc. The other way to do it is to remove the standard filter, and replace it with a clear piece of glass, allowing the camera to record IR wavelenghts. Because digital sensors are VERY sensitive to the IR end of the spectrum, the resulting images are rather dramatic and beautiful.... This is whats destined for my 350D as soon as my 5D mk 2 arrives!
Alex.