No sound output from rear speakers (Creative A500)

Hello
I recently bought Creative A500 5.1 surround sound speakers for my PC. I then bought an internal sound card as i only had 2 speaker inputs on my pc, but then found out that my motherboard has only 1 PCI slot. So i had to buy an external sound card for the surround sound to work (this one)
I connected it all up, put the wires in the correct places, but the rear speakers do not play any sound. I know they work, as I put the rear jack into the front output to test them.
If I go into sound, then try to configure it to 5.1 I don't have the option to select rear speakers. (picture of what i mean) I can't go into enhancements to select fill speakers either as the tab isn't showing up in properties.
And also, as I'm using an external sound card (USB), nothing shows up in Realtek HD audio manager, so I'm not able to do it from there.
I have searched a lot to try and find out what the problem is, and can't find anything.
Any help would be appreciated. Thanks :)

CountVeggie welcome to the Seven Forum.

Did you install the driver that came with the external or is it just running on the default Windows 7 USB audio driver? The reason your rear's aren't working at the moment is that Windows is seeing it as a 7.1 set up and not 5.1, with the rear's showing as side's.

Hi, thanks for the quick reply.
Thinking about it, I put the disk in, and the widows device driver thing came up, but I thought that the driver came from the disk, but looking at it now, there are a few files inside the disk, but none that auto install. I have tried clicking on the main install, but it says: Cannot install in 64 bit OS!
I'm guessing that this should be in a different category now, but is there any way I can solve this?