AMDI HDMI output not plugged in. HELP!

Hello everybody! I have problem that I cant solve. I have HP ENVY h8 1420t. It had windows 8 installed. I dont like it and I decided to downgrade to windows 7 Ultimate 64 bit. And since then my sound from monitor speakers disappered. I'm using HDMI cable with samsung TV monitor. I looked at playback devices and notised that my monitor was greyed out with words "AMD HDMI output not plugged in". First I thought that it was drivers problem.There is no drivers for my Radeon HD7670 video card in HP website so I decided to download it at AMD official web site. And here I've got a problem. I couldnt installed these drivers. Every time I tried to do it the errors pop out. I installed a bunch of different drivers for sound and video card from third party web sites. Nothing helped. Please help me. I've already contacted with HP support team. They dont know what to do accept install windows 8 . I dont want to do that. I hope somebody help me. Thank you!

So, you tried installing AMD Catalyst Software Suite?
Is this the page you downloaded the drivers from?
http://support.amd.com/en-us/download/desktop?os=Windows 7 - 64

Try installing the software from there.

Have you looked in your audio manager to see what device is set at default?