No dice on the windows reinstall. Still no sound in windows or bistreaming. Again, hooking anything up to the TV works fine, just not through the receiver. I'm out of ideas lol.
Which TV, make and model, do you have?
Is there any way you can get the TV to display what sound signal format it is receiving when playing windows and MC sounds?
The other possibility is that you could have an HDCP issue with the receiver. If the HDCP audio path isn't complete, Windows will not play the sound. At least that is my understanding. So when connecting directly to the TV the HDCP path is complete and everything plays, with MC playing via the receiver the HDCP path is still complete, but when bitstreaming MC sound, or Windows sounds play, HDCP fails and cuts off the sound. There may have been changes in Windows 8.1 that changed the HDCP behaviour compared to Windows 8.
HDCP can be a pain. For example, my 2560x1600 30" Dell 3008WFP monitor is supposed to be HDCP compliant and play Blu-ray discs. . . but it is only compliant when it is 1920x1080 resolution. To play Blu-ray discs on it I have to change the resolution. Annoying, and shouldn't happen, but it does.
I think there may even have been HDCP changes with Windows 8 graphics card drivers. This thread
https://forum.slysoft.com/showthread.php?57436-Windows-8-1-and-AnyDVD-HD with an HDCP problem (although different) mentions a solution of using a Microsoft driver rather than display adapter manufacturer's driver. I don't even know if Microsoft makes a HD4000 driver, although I would guess one is included in the Windows 8.1 installation. Probably Intel's own driver though. Check the driver is WDDM v1.2 (actually WDDM v1.3 for Windows 8.1), whether you have the latest and so on.
I assume that you are using the same HDMI out port and cable when connecting to the TV directly or via the receiver, and that you have tested all your HDMI cables between the known working HTPC to TV Direct. Can you connect via the receiver and output sound to the TV via HDMI? Does it work? Make sure that your second HDMI cable is good. Some older HDMI cables caused HDCP problems.
Okay. I'm just throwing out ideas. But these ideas should give you something to look into.