I call BS on that.....esp. after having run both an E7200 and a Q6600 up to 4GHz and that's with 8GB (4x2) of RAM installed.
And before you get your panties in a wad, I understand you had problems getting your OC to 4GHz, but it surely wasn't a function of the OS, as many OC'ers have been able to use Vista and achieve 4GHz and higher with it.
And who knows.....your power supply may be getting stretched out a bit.....4870's in Crossfire and overclocked, Phenom OC'd, water cooling, etc., I wouldn't be surprised that you'd be pulling upwards of 700W at full tilt.
As far as Hiper and it being great because it "overvolt a bit," sorry, but just the fact that HIPER cannot stabilize the rails on their power supplies is a sure indication of shoddy construction. If anything, a good power supply won't let the rails, no matter which one you're talking about, deviate from what it's supposed to be.....+12V, +3.3V, or +5V....at all, even under heavy stress. Overvolting of the rail by the power supply without user intervention is horrible......complete lack of proper voltage regulation. There are standards to be adhered to and to think working outside those standards is good is just silly, if not dangerous for your sensitive motherboard/cpu/gpu/memory circuitry.
