NOCD.SI

NOCD.SI is an Interleaf File played whenever the game cannot find its main assets (usually meaning the CD-ROM is not inserted). It's the only Interleaf file that gets transferred to LEGO Island's install directory, as it (naturally) needs to be accessible without the CD inserted. Its only content is a Smacker video stream.

Details
When LEGO Island starts up, it checks for  anywhere it can (usually its current working directory, or for v1.1, the , or   values in the registry). If it cannot find it, it plays the Smacker video in NOCD.SI and then exits immediately after.

If it does find ISLE.SI, it will continue trying to launch as normal, even if the rest of the files are missing. If only ISLE.SI is present, the game will softlock as it fails to find INTRO.SI (opening cutscene) and then INFOMAIN.SI (Information Center).

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 usage of the line was finalized before the game was translated to other languages, as the dubbed versions do not feature any equivalent cuts.

Unused Variants
As previously mentioned, NOCD.SI's English dialogue was edited and repurposed from a slightly different line telling players to re-insert the CD if they ejected it during gameplay. The unedited line remains in the game files, specifically in Interleaf file INFOMAIN.SI. INFOMAIN.SI also contains a second recorded (but unused) line that was ostensibly intended for the same purpose.