Open Question: why is my green audio jack very quiet?

I have windows 7 x64 and realtek hd audio manager when i plug my speakers into the green jack and pick Front speakers(I have a 2.1 system) i can barely hear anything, i have to put my speaker right next to my ear to hear but when i try using any other plug out of the 6 and pick Front Speakers - it works fine how can I fix it? Oh and if I can decide what each plug does - can I connect a 5.1 system without using the green one and instead use a different plug?