If you are the many people who just bought C-S and dosen't have HL for the mods, this could be your savior. It allows you to play Half-Life even if you only bought the Steam only version. This could be legal or not, depending on how you use this.
I'm not sure if Half-life was moved to SteamPipe,If it wasn't use GcfScape and extract your "Half-life.gcf" and follow the rest steps of tutorial
half-life.vpk or Gcf
Installed WON version of any HL mods
7Zip (opens VPKs as Zip) or GcfScape (opens GCF files)
Backed up folder of the original folder valve
Bought version of Half-Life for Steam
First: Open your half-life.vpk/gcf and extract folder VALVE to your Counter-Strike folder (for WON)
Second: Patch up your Valve folder with the Half-Life 126.96.36.199
Third: Replace all your files from the backed-up Valve folder to you newly extracted file
Fourth: Apply 188.8.131.52 or 184.108.40.206 Patch
Ways to get "half-life.vpk/gcf" without buying Half-Life from Steam.
You can: Enter your C-S CD-Key into "Activate a Product". It will automatically download the Half-Life files.
You can download Steam with all the caches (Half-Life planet and Half-Life filefront have one) But I recommend: Buy a Half-Life pack from Best Buy or Steam.
I know I sound like a charlatan, but this actually works. Just remember, REPLACE YOUR OLD VALVE FILES OVER THE STEAM FILES or your Half-Life just might not work. This is a very cheap way to obtain a WON version of Half-Life without actually buying it (for WON). I'm willing to bet that you can also obtain Blue Shift and Opposing Forces with this trick as well (minus replacing the files part). I recommend you actually buy the game from Steam (because WON versions are VERY rare) so that what you are doing is at least can be considered "legal" (in the U.S.)