Not sure if this is the right place, but hey ho
I recently had issues with a loss of internet on Win 7, IP address given was 169.xxx etc, services relating to DHCP, BFE (firewall) and others were not starting, and I was unable to start them even though administrator.
The solution that worked in my case was to open a privileged command prompt and type:
net localgroup administrators localservice /add (press enter)
net localgroup administrators networkservice /add (press enter)
Internet up and running fine upon reboot
posted here in case anyone has the same issues, whether it's one of us or a stranger looking for a solution ... apparently a Vista bug also