You can use System Restore to go back to a time before the problem started. I have to ask if you've used a so-called registry cleaner. They don't help and can cause mysterious problems.
I have windows vista ultimate SP2, on a Gateway Laptop P-173XL FX.
I used to have three types of playback devices:
Speakers, Digital Output Device (SPDIF), and HDMI.
I was connecting to the TV through HDMI, and everything was working fine.
Suddenly, my playback device HDMI disappeared (probably after a windows update I suppose), and I cannot get the computer sound through HDMI on my TV anymore.
How could I re-install that device back?