The Sub Noises
After typing in most codes you will hear a submarine radar type noise sound twice. Occasionally the noise sounds once. Here is a list of codes that make the noise sound only once:
824 (Confirmed as the first 3 numbers of the code and the length of Break and Enter)
998117526 (Someone from theprodigy.com chat went under the name '998117526'. I thought I'd try it out)
16181549725 (The word 'Prodigy' converted to numbers)
13 1 24 9 13 (The word 'Maxim' converted to numbers)
As far as I can tell, these codes have absolutely nothing in common!