I am having a similar problem to Xero - only one of the jacks at the rear of my computer seems to work, and it's a different one to the jack I used for my speakers before I reinstalled windows.
I also do not have the HD Audio Manager, and have tried reinstalling the drivers
3 times but still dont seem to have the Manager.
I may just be being a bit dim here, but where should I find the audio manager? (I've tried searching for it on my computer but found nothing?)
Do you have any other suggestions?