MSI Special BIOS for for AMD 3 core to 4 core

[Bredband71]

I have Vista 64bit and i can lock up my 550BE to B50 X4, but just before when it´s time to loggin in Windows my computer restart. Why??
I have try to raise CPU, CPU-NB and HT volt, but it will not work.
In Windows XP 32bit it´s work fine but it not stabe yet.

This is my computer:
MSI DKA790GX Platinum / AMD PhenomII X2 550BE 3.1Ghz 1.28v @ 3.6Ghz 1.28v /stepping CACYC AC 0920GPMW / Thermalright Ultra-120 eXtreme, Noctua NF-P12 Fan / 2x2048 A-Data Vitesta Extreme Edition PC8500 1066Mhz+ 5-5-5-15 2T (2.1v) / Corsair HX520W



// Tommy