And I am that mate!!
welcome mate

I built the computer and when i was fitting it together i had a few "teething troubles" The Computer does not seem to play anysound from the sockets at the back, however it is more than happy to play from the prots at the front with the USB/MIC/HEADPHONE bits.
I presume that back thingy is onboard?!
Check if you can enable your sound device in your BIOS.
Else if its like some creative stuff.. check for digital or analog output... (and what kind of speakers you got there..)
(so in any case check your settings in windows)
However in trying to activate teamspeak we found that the mic does not work. Either in the port at the front or at the back. Which is odd.
samething here.. if your sound device is onboard, and its disabled your mic wont work even...
One other thing which I have found out due to the restarting in the last few minutes is that the computer does not actually turn off. It only restarts as well. If you choose "shut down" it says that it is closing down only for the power to cut temporarily and then the whole system will restart.
These "teething troubles" seem to be turning into something more that that.
If you want the specs for the PC just ask I can get that sorted now, but in advance: thanks for this, you don't even know me and are trying to help out and I really appreciate it.
Obvious your system does shutdown, but kindly boots again (and i think its is) because you have
wake on lan enabled in your BIOS.