I cannot find a PC called Hercules V1.5. Who is this made by? You should have a sticker on your pc giving make/model number. Please try and find the info, it is far easier to offer advice when we have all the information that the right PC will give us.
You are plugging your Audio cable in to the green socket?
@ Chronos the 2nd, the PC is a TIME Hercules V1.5. The only info I have on the motherboard is from 'Motherboard resources' which says 'Device Instance Id' and has the following code underneath it: ACPI\PNP0C02\4&3656B0&0. The actual motherboard itself does not have any labels on it identifying its make, but there is a golden coloured component on the middle of the board with MSI AGP 8X on it.
Yes the audio cable in to the green socket, but the card underneath the on-board audio card must be the video card, because I later found that the VGA socket attaches to it. So there must only be an on-board audio card.