Yeah, Won is down now and forever... so only steam available (Lucky you!) So run Steam once and launch half-life from it to create automaticly all needed files.
You must download all 3 patches from
Here That is 3.0 beta 1, 3.0 beta 4 and 3.0 beta4a and install them in this order in your steam/steamapps/email folder/half-life (It should auto-target tho)
Then you can choose the game Natural Selection (beta) from your Third party mod list... If you have anymore problems, feel free to drop by #NSguides on Gamesurge.