Well I can confirm that this is really a sound driver issue.
We have two relatively new computers at home (one and two years old). When I last played Battlefront it was a month before I had the older computer hence I never tried it on these new systems (Vista) so I can't say if the older computer ever had the realtek driver or not.
The older computer, I did a clean install of Windows 7 (x86). My story for that issue is above so I won't repeat it. About a week later, I simply did an upgrade on my wife's computer (the newer one) as there was little things on it. When the upgrade was done and the final restart was done - upon startup I noticed the Realtek icon for sound. It didn't occur to me that I may of deleted a driver that was already there on the older computer but because of "newer" drivers it won't allow me to see the options that the realtek driver would.
So, this morning I decided to install Battlefront II on my wife's computer to see if it would work.
From what a lot of sites had mentioned I went to: Control Panel\Hardware and Sound\Manage Audio Devices. I then clicked on the "Recording" Tab, right clicked on the white area of the selection window and checked "Show Disabled Devices".
Needless to say, a Stereo Mixer popped that was disabled. I enabled it, applied it, closed all that and started up Battlefront II. It was working fine with sound and everything; single player and multiplayer. I didn't even have to do any compatibility tabs.
Hence I have one computer with Win7 that Battlefront II works with and the other not. I tried downloading and installing the realtek drivers but it doesn't seem to work so I'm not too sure what to do for the computer that it doesn't work on anymore. The driver is the issue/solution that is for sure.