My PC is having 7 channel sound card output called 7.1. I am having 5.1 speaker system. Can I connect this to my PC and if yes how?

The first number is how many speakers.. the second is the subwoofer... and yes... there should be a way to set it to 5.1 unless you have 7 speakers...

A 7.1 system consists of front R,L speakers, a center channel, R & L side speakers, R & L rear speakers and a subwoofer. A 5.1 system is the same except for the side R & L (it does not have these). To answer the question yes, you can connect a 5.1 channel system to a 7.1 channel soundcard, almost all are compatible. You will need to connect the sound card to a sound system which includes an amplifier. This can be connected usually through an optical or Toslink connector, though most cards have line level outputs which can also be conncted (but that's a bunch of wires). Good luck and consult your owners guide, because everyone is a little different. ~ G