Recover mac mini broken BIOS (mac mini displays nothing) Well, month ago I gave mac mini (late 2011) to my little brother with new HDD and RAM memory stick. So, being an independent person, he has tried to install Windows on empty HDD (yeah, it's weird) and after his several tries mac mini stopped showing anything on screen. Mac mini still working, boot up signal and light are on, but now we have nothing on display, like nothing is connected. 
In workshop repairer said that young man broke BIOS and recover costs 7 000 rub (~106 usd), what is pretty expensive to us. Is there any way to recover bios on my own? In case that I don't see anything on screen while mac is working. :D
Thanks in advance!

UPD: Brother just burned .iso file on DVD and inserted in mac mini. How installation had even started - I have no idea. But it failed.
I erased entire HDD. Have tried all the startup key combinations (reset PRAM, etc). Nothing reanimated mac mini. On booting up I have "no signal detected" screen.

UPD2: Tried several monitors and HDMI cables. Mac mini still displays nothing and without HDD too.
If you are entirely sure that the computer is starting up with a connection to a monitor, then this is a problem with the disk format more than likely. This will make it so that the Mac will not be able to boot into recovery either. You'll need to go to an Apple retailer to ask them to reformat the disk for you, or perhaps it's possible on your own. I know that apple likes to ensure no third-party computers register with Mac OS X so they format the disks in dumb way.