Load handling while using ffmpeg.exe

I am using ffmpeg.exe in my project to convert the uploaded video files(.wmv,.mov,.avi etc) to flash movies files (.flv). I have used process.start() method to execute the executable. In such a scenario every time a file is uploaded, a new process is created for the ffmpeg.exe which converts the uploaded file. This will increase the load on the server as the number of user increase. How can overcome this problem? Can anyone suggest some way out