You guys are very helpful, thank you!
Couple of things I should mention on the GPU:Yesterday evening I got a mouse graphics glitch in Windows, where the pointer appeared like this:

Immediately I DDU'ed the older driver of the RX480 and I installed the latest one: Crimson Edition 16.7.3
http://support.amd.com/en-us/download/desktop?os=Windows+7+-+64That fixed the mouse pointer, but after the new driver install, I noticed last evening, that while watching YouTube in full screen, my mouse froze a couple of times, then resumed after some seconds. Once I even heard the USB sound of disconnecting and reconnecting (the mouse is a standard USB - nothing special).
On the HDD:I will try 2 things today, before considering a new HDD;
- Will run chkdsk today, test the WD Black 2 and performance afterwards;
- And will also try out running my old PC's HDD which I still have - Seagate Barracuda 500 GB, which is a SATA2 7200 RPM druve, to see how the rest of the hardware will run games off of it (without the WD Black plugged in) - I still have a Win7 Enterprise installed there and games installed.
Will come back after I test the HDDs later today.