You will probably want to

[RehabMan]

You will probably want to just turn that behavior off.  See Power Options in the Windows Control Panel.  Generally,  you don’t want Windows to be turning off your display when it detects idle.

In your case, I don’t think the standby helper app mentioned above will do you any good for the occasional black screen when your TV/amp turns back on (ie. even though your PC is never sleeping, your TV/amp are going into standby which tends to cause the same HDMI handshake issue with the WMC app.)… You should probably look into what I’m doing which is to shutdown and restart WMC as appropriate (ie. when you turn on / turn off your AV system).