if you have an HDMI capable receiver I am going to assume you have at least a 5.1 setup correct? And I am also going to assume that "HW is a motherboard with HD3200" means onbaord HD3200?
If yes then I would suggest using either the coaxial output or optical S/PDIF output to the receiver as you are not reciveing 8 channel LPCM through HDMI.
As to your actual problem I am setup same as you, however I am not having that problem... is video still able to pass through to your TV even in the audio not plugged in state?
My Computer
At a glance
Windows 7 Ultimate x64 RTMAMD Athlon II X2 240 @ 3.2Ghz6GB Mushkin DDR3 PC-1333ATI Radeon HD 4200 IGP Hybrid CrossFireX w\ S...
Computer Manufacturer/Model Number
Home Built
OS
Windows 7 Ultimate x64 RTM
CPU
AMD Athlon II X2 240 @ 3.2Ghz
Motherboard
Gigabyte GA-MA785GMT-UD2H
Memory
6GB Mushkin DDR3 PC-1333
Graphics Card(s)
ATI Radeon HD 4200 IGP Hybrid CrossFireX w\ Sapphire HD3450
Sound Card
Onboard Realtek HD audio controller
Monitor(s) Displays
D-SUB: LG W2343T-PF 23" LCD HDMI: LG 32LH20 32" LCD
Video is fine with ati 9.10 and realtek 2.35 hdmi audio drivers. I can get ac3\dts audio from the hdmi cable connected to "hdmi 1" on the receiver.
The problem is when switching to tuner, tv etc and back. The HDMI audio out is stated as "not plugged in" and ATI complains about a HDMI-DVI cable incorrectly. So realtek digital output is set as default.
Changing resolution or turning on\off tv and receiver brings it back.
Tried a vista image made before win 7 and it worked fine, ac3\dts output and the receiver recognized it fine after switching to other sources.
Spend a few hours with a clean image of win 7 and tried different combinations of ati\realtek hdmi drivers. Either would the screen be black or the hdmi audio was not plugged in. So im guessing something with how hdmi devices recognize each other that changed in win 7.
What receiver are you using? I have been switching inputs all morning at break neck speed and can't replicate this problem... using same drivers. only difference hardware wise is I am using the 785G chipset.
As for your audio just be aware that it is only 2 channel going through HDMI.
My Computer
At a glance
Windows 7 Ultimate x64 RTMAMD Athlon II X2 240 @ 3.2Ghz6GB Mushkin DDR3 PC-1333ATI Radeon HD 4200 IGP Hybrid CrossFireX w\ S...
Computer Manufacturer/Model Number
Home Built
OS
Windows 7 Ultimate x64 RTM
CPU
AMD Athlon II X2 240 @ 3.2Ghz
Motherboard
Gigabyte GA-MA785GMT-UD2H
Memory
6GB Mushkin DDR3 PC-1333
Graphics Card(s)
ATI Radeon HD 4200 IGP Hybrid CrossFireX w\ Sapphire HD3450
Sound Card
Onboard Realtek HD audio controller
Monitor(s) Displays
D-SUB: LG W2343T-PF 23" LCD HDMI: LG 32LH20 32" LCD