: Using this version without additional Extended Security Updates (ESU) may leave the server vulnerable to threats discovered after early 2020. Technical Capabilities

SP1 brought Dynamic Memory, allowing administrators to pool available memory on a physical host and distribute it dynamically to virtual machines based on current workload needs.

: Some proprietary business software or older versions of SQL Server literally cannot run on anything newer.

The string windows_server_2008_r2_sp1_x64_esd_en-us_jan_20_full refers to a specific, digitally distributed build of Microsoft’s enterprise server operating system. While Windows Server 2008 R2 was released in 2009, this particular variant marks a later, optimized refresh: Service Pack 1 (SP1) , delivered in the ESD (Electronic Software Download) format.

: This ISO contains the complete operating system, not just a patch or upgrade file.