Vista - COD4 iw3sp.exe stopped working

I found the older threads about this problem but their solutions did not help. I didn't even realize that COD5 was out, man I'm behind the times....

At any rate, I have a dual-boot Vista64/XP32 machine, and I installed the game (COD4) into the same directory under both OS's. It works fine under XP, but won't even start under Vista64. As soon as I click the icon to start the single-player mission, I see the splash screen then "iw3sp.exe has stopped working". I have tried a number of the offered solutions, but was wondering if anyone else had anything to offer.

1). Game has latest patch
2). I have updated my Realtek sound drivers to the recently released 2.32 versions.
3). I don't have that little folder icon other people are referring to in my Realtek Manager software so I can't select "disable front panel jack".
4). I tried plugging in USB headphones and making them the default audio device.
5). I tried plugging in headphones (3.5 jack) into the mic jack on the front panel.
6). Have installed latest nvidia graphic drivers.
7). Have flipped my BIOS setting for the front panel from "HD Audio" to "AC97" and back again (after reboots in between and attempts at launching the game).

Have tried a few more things, but can't think of them right now. My system is the following :

Core2Duo 2.4 Ghz
Asus P5N-E SLI mobo
Chipset : nVidia nForce 650i SLI SPP
4 GB RAM
8800 GTS 320 MBs vid card
onboard Realtek ALC883 5.1 sound

As I said, I can play the game under XP, but this is the first time I have had to reboot into XP in months. Took an hour just to apply all the missing patches it has been so long :-). Would prefer to get it going under Vista64. Tonight I will try uninstalling completely the Realtek drivers and letting Windows install MS ones, but I won't hold my breath.

Anyone else get this going under Vista64 with onboard Realtek audio?

Thanks,
DD.