The first direct expansion following the events of HL2.
The original 1998 classic ported to the Source engine. Half-Life 2: The groundbreaking sequel. Half Life - Source Quadrilogy [FitGirl].zip
The is a highly popular community-curated repack that compiles the core "Source" engine era of the Half-Life series into a single, highly compressed installer. The first direct expansion following the events of HL2
Most FitGirl repacks include a MD5 tool to verify the integrity of the files before installation to prevent errors. Half Life - Source Quadrilogy [FitGirl].zip