Dell :: Audio M1130 After Windows 7 Upgrade

I installed Windows 7 64 bit on my ~2 year old m1330 laptop and now I have the following issues with audio that I haven't found a solution for:

1. The internal speakers don't work at all.
2. Only the left headphone output works, not both as before the upgrade.
3. When I have both headphones and HDMI plugged in, I have to use the Sound control panel to set one or the other to default (with the "Set Default" button) to switch which one gets the audio.

I'd prefer that it be automatically switched to headphones when I plug them in, and back to HDMI when headphones are not plugged in, but I've not found any way to make this happen. In fact it would be even better if both headphone and HDMI audio were active simultaneously