The eMachines T3604 desktop computer uses an Intel 945GCL motherboard,http://www.ascendtech.us/intel-d945gcl-1066fsb-ddr2-pcie-x16-sata_i_mb4intd945gcl.aspx
(No, not advertising. Just a good photo of the motherboard, if you slightly scroll down)
Look at the chart below the photo of the mobo. (MOtherBOard)
A) Two PCI slots (Two PCI Conventional bus connectors. Long white slots)
B) One PCI Express x1 bus add-in card connector.
(PCI Express x1 slot. The longer PCI-Express x16 slot is on top.
Then the two long white PCI slots. Then the shorter black PCI-Express x1 slot)
You can use a Sound Card in an available white PCI slot, or if the black PCI-Express x1 slot is open.
Yes, I know, I'm getting to it, lol!
The Onboard Audio -> Intel High Definition Audio, doesn't have an output mixer feature.
My onboard audio - Realtek, (And on an Intel mobo), does.
[ Intel 915G (Southlake) motherboard.
Has a Realtek audio chip, ALC860. I use the Realtek Audio Manager. Has Sound Effects, and an equalizer.
What happened from the Intel 915G to the Intel 945GCL INTEL?
Suggest this if you have an open, available PCI slot,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4459743&CatId=2771
This, if you only have the PCI Express x1 slot open,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=420799&CatId=2771
I don't recommend a USB sound card, but you may,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=5344879&CatId=2771
(Usually only 16-bit.
Plugs into a USB port where the contacts are not gold plated, as on a PCI sound card, or PCI-Express x1 sound card.
I'm old school, and probably need to evolve ; )
Plus use Virtual DJ,http://www.virtualdj.com/download/free.html