avg_free_stb_all_8_32_cnet.exe is 828KB only which is AVG download manager. I suggest to try to download the full installer of AVG Free from http://filehippo.com/download_avg_antivirus/ (click Download
Latest Version at the right side of the page to download 65.39MB which is the full setup file of AVG free.

BTW, I just tried downloading from CNET http://download.cnet.com/AVG-Anti-Virus-Free-Edition/3000-2239_4-10320142.html
The avg_free_stb_all_8_32_cnet.exe launched AVG download manager with option to install AVG free edition or 30 days trial of AVG Internet Security.
What browser do you use to download the software?