At that time, the operating system of choice was Windows 2000 or Windows XP. The concept of a "64-bit" consumer desktop was a distant speck on the horizon. The Oracle 9i client was written, compiled, and optimized for a 32-bit architecture world. It knew nothing of the security protocols, the kernel structures, or the memory addressing that would define Windows 10 nearly 15 years later.
Oracle Instant Client Downloads for Microsoft Windows (64-bit) Oracle 9i Client Download For Windows 10 64-bit
Search Windows for "ODBC Data Sources (32-bit)". Yes, you must use the 32-bit ODBC Administrator ( C:\Windows\SysWOW64\odbcad32.exe ). Add a new System DSN using "Oracle in Ora9iClient". If it validates, your legacy application will connect. At that time, the operating system of choice