I have an Athlon based Asus motherboard with built in ATI 4500. I tried connecting it to my Samsung pn58c8000 through HDMI with no other monitor hooked up. It shows post on the TV and if I go into the BIOS I can access everything fine. Safe Mode works without a problem (full display). In normal mode it boots until Windows 7 Professional starts. It shows the progress bar, but when the Windows 7 logo is supposed to come up, it blanks out and that's it. Anyone have any suggestions?
A few thoughts:
Have you installed the latest ATI drivers to make sure? Also plug in a DVI or VGA just for testing purposes.
Right click desktop > Screen resolution
Then click Detect on the top right.
You should see some extra screens on the view.
There is a drop down box showing display devices, if your HDMI device is listed select that and choose it as your primary display.