I have tried some other forums, but no luck. You are my only hope ... 
Here are my specs:
PC = Gateway SX2800 (http://www.gateway.com/systems/product/529668287.php)
Processor = Intel® Core™2 Quad Processor3 Q8200 (2.33GHz, 1333MHz FSB, 4MB L2 cache)
OS = Genuine Windows Vista® Home Premium (64-bit) with SP1
Memory = 4096MB 800MHz DDR3 Memory (2 x 2048MB Modules)9
Motherboard = Systemboard with Intel® G43 Chipset + ICH10
Video = Integrated Intel® Graphics Media Accelerator X4500 (VGA,HDMI)
Video Driver = v. 7.15.10.1829 (upgraded from factory install 7.15.10.1666)
Monitor = Asus VW246H. VGA,HDMI,DVI. HDCP (http://usa.asus.com/product.aspx?P_ID=zMRyN4KB5o5rSqKr&content=specifications)
Here are the facts:
1) I have both PC and monitor powered down. I connect HDMI cable as the only monitor. Power up. Monitor is on HDMI input, and reports "HDMI NO SIGNAL" with a blue screen.
2) Asus monitor and HDMI cable video and sound work fine when I connect it to my Roku video streaming box.
3) VGA input of Asus monitor works fine.
4) I connect a dual display with an old VGA monitor as primary display extended to Asus HDMI as secondary. Intel Graphics proerties window shows that both displays are detected: "monitor" for VGA primary display and identifies Asus HDMI display as "digital television". But I still have the "HDMI NO SIGNAL" with a blue screen.
5) The PC came factory installed with Intel driver 7.15.10.1666. I upgraded to latest driver 7.15.10.1829. Both drivers see the "HDMI NO SIGNAL" with a blue screen issue.
Here are my questions:
1) Does anyone know what is going on?
2) Does anyone have a driver for x4500 that works with an HDMI display? Should I downgrade?
Thanks for any help or suggestions.

Here are my specs:
PC = Gateway SX2800 (http://www.gateway.com/systems/product/529668287.php)
Processor = Intel® Core™2 Quad Processor3 Q8200 (2.33GHz, 1333MHz FSB, 4MB L2 cache)
OS = Genuine Windows Vista® Home Premium (64-bit) with SP1
Memory = 4096MB 800MHz DDR3 Memory (2 x 2048MB Modules)9
Motherboard = Systemboard with Intel® G43 Chipset + ICH10
Video = Integrated Intel® Graphics Media Accelerator X4500 (VGA,HDMI)
Video Driver = v. 7.15.10.1829 (upgraded from factory install 7.15.10.1666)
Monitor = Asus VW246H. VGA,HDMI,DVI. HDCP (http://usa.asus.com/product.aspx?P_ID=zMRyN4KB5o5rSqKr&content=specifications)
Here are the facts:
1) I have both PC and monitor powered down. I connect HDMI cable as the only monitor. Power up. Monitor is on HDMI input, and reports "HDMI NO SIGNAL" with a blue screen.
2) Asus monitor and HDMI cable video and sound work fine when I connect it to my Roku video streaming box.
3) VGA input of Asus monitor works fine.
4) I connect a dual display with an old VGA monitor as primary display extended to Asus HDMI as secondary. Intel Graphics proerties window shows that both displays are detected: "monitor" for VGA primary display and identifies Asus HDMI display as "digital television". But I still have the "HDMI NO SIGNAL" with a blue screen.
5) The PC came factory installed with Intel driver 7.15.10.1666. I upgraded to latest driver 7.15.10.1829. Both drivers see the "HDMI NO SIGNAL" with a blue screen issue.
Here are my questions:
1) Does anyone know what is going on?
2) Does anyone have a driver for x4500 that works with an HDMI display? Should I downgrade?
Thanks for any help or suggestions.