You can sometimes find the original Sun download pages backed up at archive.org . Look for j2sdk-1_4_2_03-windows-i586-p.exe (Windows) or the Linux .bin version.
Installing JVM 1.4.2_03 on a modern Windows 10 or Windows 11 machine will fail. The installer is a 16-bit stub or a 32-bit legacy installer that will be rejected by modern Windows Kernel security. Download Sun Java Virtual Machine -jvm- Version 1.4.2 03
Maintaining "frozen" development environments for old hardware or embedded systems. Technical Specifications Release Name: J2SE Runtime Environment 1.4.2_03 You can sometimes find the original Sun download
Are you getting a specific when trying to run your app? The installer is a 16-bit stub or a
Released by Sun Microsystems in the early 2000s (specifically, this build hit the streets around Q4 2003), J2SE 1.4.2_03 is ancient history in tech years. But in the real world, it is still the heartbeat of specific ERP systems, medical devices, or industrial control software.
Before you hit that download button, understand the danger.