Nem's GCFScape 130 Full
^ this is the prog you need.
http://www.slackiller.com/hlprograms.htm^Get it on this page.
You can also get this address on the links page for TWHL located on the left of this window.
The problem you have is that the guys over at valve thought it would be cute to recently start putting all the files for HL & CS etc. into a special brand of archive file called a GCF file.
My guess is that using these files allows easier mechanics for the new "check resource file integrity" tool in the STEAM prog.
Unfortunately, this method makes it damn near impossible to access stock HL/CS textures, sounds, sprites, etc. without an external tool.
Fortunately, A tool has been made. I have yet to experiment with this tool because I have just recently encountered this problem.