This is a nice full-featured source port of original Doom. The best features are OpenGL support with some nice lightning effects, multiplayer gaming support and availability for DOS, Windows, Linux and OS/2Warp systems.
Download and unpack port files to the original game's directory ('d:\games\doom' in my case). Run 'launcher.exe' to start the game. If you have done everything right, then you will see the following screen:
Press 'OK' to start configuration process.
Browse for 'Doom Legacy' executable file (its location was 'D:\Games\doom\Legacy.exe' in my case). Select a WAD file you would like to use. WAD files are main resource files for the Doom-engine games, and they are usually located in the same folder with all other game files. You can specify more than one WAD file if you'd like to.
The main menu of Doom Legacy Launcher will appear. Click 'Setup' to open 'Advanced Setup' screen.
Set 'Render mode' to 'OpenGL' and check 'Use Direct Sound 3D' checkbox.
Press 'OK' to return to launcher's main menu.
Click 'Launch' to start game.
Open 'Options' from game's menu. Turn on 'Always run' option, set some crosshair and disable 'Auto-aim' for the best gaming experience.
Open 'Options'->'Video Options'->'Video modes' from game's menu. Select most suitable video resolution and make it default by pressing 'D'.
Open 'Options'->'Video Options'->'3D Card Options' from game's menu. Set 'Mouse Look' to 'Full', set 'Quality' to '32 Bits' and select 'Trilinear' in 'Texture Filter'.
Open 'Options'->'Mouse Options' from game's menu. Set 'Always Mouselook' to 'On', disable 'Mouse Move' and adjust 'Mouse Speed' and 'MLook Speed'.