Random crashes can also be caused by a faulty ram. Download, unzip and burn memtest86+
's bootable .iso image file using a burning software that can handle .iso files. Enter the BIOS at startup and set the boot priority to CD-rom first. Boot on the CD, leave memtest run overnight and report if it finds any error.
Also test the system drive for errors : start => run => chkdsk c: /R. You'll be prompted to restart the computer. Tell us about the scan's results.
The voltages in the BIOS seem ok but as dai said your BFG power supply is not a very good quality one (it's manufactured by topower which made crappy power supplies in the past). See if you can get your hands on another 800W power supply to test your computer with it.
and check that the voltages remain stables within Windows. If the +3.3, +5 or +12V line fluctuate then you'll know you'll have to get a new power supply.
The system specs you provided don't tell us much. nForce and GeForce are not the brands, it only means that your motherboard and video card have nvidia chipsets. Look on the hardware parts themselves or on the box they came in (brands are XFX, eVGA, Gigabyte, Asus, Asrock, ... for instance). We also need to know about your hard drives, CD drives, other PCI cards and RAM. If you have 3 PCI cards and 4 hard drives it'll add to the load on the power supply.
Please click on the posting system specs link, install the free everest version, create a .txt hardware report using the report wizard and attach that file to your next post using the manage attachments button (lick on post reply or on go advanced). This will tell us all there is to know about your hardware.