As the topic states:

I start my PC as usual, POST screen shows up, ram and everything else gets tested just fine, but then the screen goes black. No listing of IRQs, connected HDDs, zip. Windows isn′t starting.

Resetted CMOS already, switched GPU, removed HDDs and RAM just to be sure, disconnected my DVD-Writer. Would appreciate any help in narrowing it down.

You could try booting from a Linux USB and see what that does. E.g. take a look at the boot drive in gparted.

At this point, see if it will boot to a boot drive like a USB stick or a Optical Disk.

However, what worries me is you see no "Missing OS" or similar error, and you see no missing HDD error message. This could mean that your Mobo is on the way out.

Another thing you can try, and hopefully this fixes it, is to restore the MBR

http://support.microsoft.com/kb/927392