If your organization has a Volume Licensing agreement, this is the safest source. You will find the exact SHA-1 hashed ISO.
Avoid downloading ISO files from unofficial third-party websites, as these often contain malware or pre-compromised installers. Sql Server 2008 R2 Iso
Surprisingly, MSDN subscribers often have access to older software libraries. If you have a Visual Studio (formerly MSDN) subscription, check the "Downloads" section. Microsoft has historically kept a "legacy" section where subscribers can grab older server OSs and SQL versions for backward compatibility testing. If your organization has a Volume Licensing agreement,
from the mounted drive to open the SQL Server Installation Center. New Installation Installation from the left pane and choose Surprisingly, MSDN subscribers often have access to older
Because Microsoft has transitioned focus to modern versions like SQL Server 2022, direct official downloads for the full Standard or Enterprise ISOs are increasingly rare.