Windows 7 goes to sleep when HDMI monitor is turned ON!

Hey guys, I'm wondering if any one can assist me with a fresh install of Win 7 Ultimate x64 on my HTPC.

• The issue is this, the HTPC remains on at all times.
• Every power saving feature I can find is turned off. Monitor is set to never turn off, pc is set to never go to sleep. In advanced power setting HDDs are set to turn of after 99999 minutes, never turn of network adaptors or put anything to sleep ever.
• I have also been to device manager and selected never turn off network adapters (just in case)
• I use my remote to turn on my TV and AMP. HDMI signal to TV and optical audio to AMP - no HDMI pass through of AMP.
• When I switch OFF the AMP and TV the computer stays awake no problems. If it has been a few hours and I return and switch the TV and AMP ON the PC goes to sleep! I then need to use the power button on the pc case to wake it up again.
• If I turn the system off and back on immediately, the pc stays powered on. It only arises after a few hours. (not sure how long exactly

This makes no sense, why would Win 7 go to sleep when it gets and HDMI signal?

Any help would be appreciated. Cheers.

Cheers for the reply. Not long after I posted this I remembered a little program called HDMIYo! It resets the 'handshake' between HDMI devices in windows (that is my 'I know nothing about how this actually works explanation').

Anyway, I haven't had the issue since installing it. So I guess that was the fix.