if you want to play with this annihilus-mod, you will be in need of running the videotest again (its .exe is found in your diablo 2 lod folder). This time set the option called d2fx glide (something with glide...)
then restart your whole pc, and try to start the annihilus launcher.
side question: have you updated your game to 1.13d before installing annihilus mod? You normally have to login to battle.net with a fresh vanilla installation, to get the download + install started. If you havent done this, try to reinstall Diablo 2 and do the 1.13d update before downloading annihilus... pls.
If you have further trouble installing / playing, wait for game or acyroma to post in your topic
hope this helps!
regards