Thank you so much for being so proactive in helping people! Concerning the "pure" keyboard problem I must now select as best answer the last tip by Daveincaps. I spent a bit of time getting to the office and back for taking home the USB keyboard, and this was the magic, in my case.
I scratch re-installed Windows 7 and now I am able again to access the BIOS with a single nice F2 stroke on the nice PS2 keyboard, without any gymn suggested elsewhere (press all keys, make strange things...).
The only "little" remaining problem is that... with fresh (and not online yet) Windows, the computer is still not working properly. Something never seen before. 15 minutes for booting windows and 15 minutes for shutting down. I'm sorry, because, before the wineHQ incident (and I cannot really really realize how such a piece of s...oftware was able to crash things such as a low level...) the machine was quite well performing (I was making data mining with R and Numpy on "big data" sets).
Now, as I can access the BIOS, here all the details requested by riider:
ASRock BIOS version N68C-S P1.20
When started up there is this series of messages, the last one is nasty:
SATAII_1: SAMSUNG HD103SI 1AG0111B
Ultra DMA Mode-6, S.M.A.R.T. Capable and Status OK
SATAII_2: TSST Corp CDVDW SH-S223C SB02
Ultra DMA Mode-5
SATAII_3: WDC WD5000AAV-00ZTB0 01.01B01
Ultra DMA Mode-6, S.M.A.R.T. Capable but Command Failed
Now: as I am very far from this "low level things" if you can give some more suggestion I will be very thankful. This is now OOT here, so if needed I open another thread.
In particular should I reset the BIOS to the default settings?
There is something called "Overlock Mode": should I make anything there?
Should I make an update? Is the ASRockInstantFlash the way to make it?
There is a setting called "Performance Setup Default". Should I use it?
If you are so nice to get me on the right path, it would be great!