NOCD.SI

NOCD.SI is an SI file. It's the only SI file that gets transferred to LEGO Island's install directory, the rest remain on disc. It contains a stream.

Details
Officially, NOCD.SI is played whenever the LEGO Island disc is not inserted. Specifically, it plays when it cannot find  in either the "diskpath" or "cdpath" (having   without the other SI files will cause LEGO Island to softlock on startup, but will not display NOCD.SI).

The three second video features the Infomaniac who charmingly tells you that there is no CD inserted:

The dialogue in NOCD.SI was originally intended for the CD being ejected during gameplay, but has been edited and repurposed in NOCD.SI. The original unused voice clip still exists in the game files, revealing the full line to be: "Whoops! You have to put the CD back in your computer." The version of this line in NOCD.SI crudely edits out the word "back" to change its meaning. Instead, in the final game, ejecting the disc during gameplay causes the game to crash. Perhaps the developers were unable to implement this functionality and the original line would have been used if they could.

It seems this line was finalized to only be played if the game starts up without a CD before the game was localized, as the dub versions do not have this cut.

Unused Variants
As previously mentioned, NOCD.SI's English dialogue was taken from an unused variant of it, still present in the game's files. This unused variant lies in INFOMAIN.SI. Also present in INFOMAIN.SI is dialogue of the Infomaniac who also tells you to put the CD back into the computer, but in a completely different tone and manner. It's likely this dialogue was also scrapped for the same reasons as the former.