It was designed for Windows XP and 2000, but can theoretically run on newer systems like Windows 10 using compatibility modes. Modern System Compatibility
If you decide to download from a site like the Internet Archive: Microsoft Office 2003 Portable Download WORK
The desire for a portable Office 2003 is essentially a desire for what the modern "Cloud" now provides. Today, tools like Office Online Google Workspace It was designed for Windows XP and 2000,