[Bahman]

Do this work:
Go to "Start" and then search for "Run" and when is found, click on "Run". Write this, there:
"rtmpdump.exe path" -r "your rtmp link" -o "output file name.flv"

For example, I have put rtmpdump.exe in a folder in my desktop. So "rtmpdump.exe path" is: C:\user\name\desktop\folder\rtmpdump.exe