ISLE.EXE

ISLE.EXE is the main frontend of LEGO Island. It contains very little actual game code, mostly handling window initialization and the event loop, and passing off to LEGO1.DLL for everything else.

Its simplicity is demonstrated in its file size, only 85KB compared to LEGO1's over 1,000 (unless your copy shipped with SecuROM, in which case ISLE will be much larger). However, it does handle a number of crucial responsibilities that are worth documenting.

SecuROM

Main article: SecuROM

In at least one version of LEGO Island, ISLE.EXE was found to be protected with SecuROM. SecuROM is a form of DRM/copy protection, controversial due to its heavy-handed malware-like approach. Additionally, due to improved security measures introduced in Windows 10, SecuROM protected games no longer work at all on modern versions of Windows, requiring a cracked or patched version to play those games.

Since no other copies that we know of ship with any DRM whatsoever, it's unclear who decided to introduce SecuROM on this specific version and why. The actual frontend code, as well as that copy's LEGO1.DLL, was unchanged, so simply replacing ISLE.EXE with an unprotected copy from another version will bypass SecuROM entirely.