While the technical reasons for needing this specific version are understandable, the security implications are profound. Searching for puts an organization in a precarious position.
FortiClient 4.2.0 is End-of-Life. This means Fortinet no longer supports it. There are no security patches, no bug fixes, and no signature updates FortiClient V.4.2.0.0250 Download
Once you have obtained the installer, follow these steps: While the technical reasons for needing this specific
Do not install this version on any machine connected to the internet or a production network unless it is an air-gapped, legacy industrial machine running Windows XP/7 (32-bit). no bug fixes
to resolve network startup delays or DHCP acquisition issues commonly found on Windows 7 systems during that era. Download and Installation Guidance