MMRES_DE.DLL installed with eCS 2.2 beta. Back at the time, I chose the installation in german.
Maybe you need to look into the CWMM install package to find it (but I don't know where you find that on the DVD, eCS or ArcaOS).
If you want to experience the "sudden system reboot", what you can do is to back up mmres_en.dll, lxlite /x the DLL, use a hex editor to change the internal module name from MMRES_EN to say MMRES_DE and save back.
For once that will prevent the DLL from loading. But if you try often enough (by invoking volume.exe multiple times, say 10 times) it will eventually take down your whole system.