Do you have the bios for Vista installed? I think it's 3.18?
I've not had any issues with my m9700, but I'm still using XP on the platform. It was designed, built and sold with XP as the OS, with upgrades to Vista near the end of it's run. I chose not to move to Vista due to the memory requirements, and the dreadful condition of Vista and it's issues when it was released.
Having said that, since AW did support Vista for the platform, it should be functional. If you're having problems with coming out of sleep/hibernation, I've seen people here that had that problem due to the video drivers they're using. I've not seen the SLI issue at all.
I would make sure you have the 3.18 bios, then reinstall Vista with the drivers AW certified in the order they use at the factory, especially the chipset and vid card drivers if you're still interested in trying to get it to work. There have been some issues with XP on the m9700 when the drivers are installed in a different order than AW does at the factory.Here is the drive install order as listed by AW.
If you're using a dual boot setup, there are several posts on these forums regarding how to install, which OS to install first, and how to get it working without conflicts. Dual boot setups can be problematic due to conflicts in the boot sector.