As you know I HATE custom sounds when I am trying to play. CSS has a filter for this (cl_downloadfilter nosounds) but this isn't available in 1.6. Also deleting them will just make your client re-download them.
(Warning! DANGEROUS if instructions are not followed EXACTLY)
I couldn't get it to work any other way except putting the file into the directory itself, if you run this file in any other directory it will destroy every file in that directory. I am not responsible if you mess your things up.
Open notepad and paste the following
for %%f in (*) do copy NUL > %%f
Select File, Save As
Move into your CS Misc Sound directory (C:/Program Files (x86)/Steam/steamapps/username/counter-strike/cstrike/sounds/misc)
File name: sounds.cmd
Save as Type: All Files
Now just double click the newly saved file. The files will stay there but the file sizes will change to 27 bytes. Counterstrike will still play these files, but since they contain no data nothing will happen.