I had just installed a Asus ATI Radeon EAH5450, utilizing the HDMI port. The computer booted fine, and everything looked great up until just after the "Starting Windows" screen in Windows 7. Then when it came to my sign in and desktop everything had a pink/purple hue, and the display was being underscanned, and not filling up the tv. I scoured the net for a soulution but found absolutely NOTHING. Kind of irritating. I downloaded fresh drivers, and that still didn't help. Finally after going though every setting in CCC, (Catalyst Control Center) I discovered the Pixel Format setting. I changed it from 4:4:4 YCbCr to 4:4:4 RGB and that solved the problem. I then went to the Scaling Options tab and changed the Underscan/Overscan to 0% and it nicely filled up my screen.
Detailed solution.
1. Open CCC
2. Select Desktops and Displays from the Graphics dropdown menu.
3. Right Click your problematic display from the "please select a display" selection and select Configure
4. Tab over to the end tab and change the Pixel Format. Try going from YCbCr to RGB, thats what worked for me.
5. The Scaling options tab allows you to resize the screen to fit the display.
6. CCC could be built better to be more navigation friendly, but hey, who's perfect.
With that problem fixed, It was time to figure out why the audio over HDMI wasn't working. After installing more drivers for ATI Hi Def Audio, and still no fix, I decided to just go ahead and start from scratch by doing a system restore. Back to square one. But I figured that I knew how to fix the pink/purple and could zip through the reinstall of the graphics card quickly. So system restored, drivers installed, and guess what, no pink/purple problems this time. Weird. But still no audio.
Being extremely fed up, I re-opened the ausu box, pulled out the static proof bag and pulled my computer from the wall, ready to rip this darn thing out and send it back. But when I bumped the HDMI cable, I heard a noise through my speakers. It wasn't much, but it gave me hope. I then pushed the HDMI cable into the HDMI port alot harder than I though was necessary, and it went "Plunk". The HDMI Cable wan't seated properly. With that done, the audio worked fine. and I knew alot more about graphics cards.
I hope this will help others.