STRAIN is a 32-level partial conversion released in 1997 by the Alpha Dog Alliance. It features nine new or modified monsters through the use of DeHackEd, and a soundtrack written by David "Tolwyn" Shaw, Mark Klem, and Jon Landis.
Total classic. The enemies, the soundtrack, the experience
One of the most original partial conversions ever made
To install (for Windows):
Open a command prompt window and navigate to the folder you unpacked the .zip to, then type this command:
copy /b strain.001 + strain.002 + strain.003 + strain.004 strain.exe
Run strain.exe in a program like DOSBox (http://www.dosbox.com/), then run strain.bat to install it.