Need advice configuring custom built destop

So I recently built my first desktop. It is really fast and runs great most of the time. However every once in in while, usually after being on for a while or trying to run a more intensive program it will just freeze. There is no error message displayed and I am forced to do a hard shutdown. After doing some research I believe the issue is due to some BIOS settings, such as voltage, timing, frequency, etc... I am new to this environment and need some advice as to what values I should use.

My machine:

XFX MBN790IUL9 LGA 775 NVIDIA nForce 790i Ultra SLI ATX Intel Motherboard
OCZ Obsidian 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
Rosewill Green Series RG700-S12 700W
Intel Core2 Quad Q9400 2.66GHz
Western Digital Caviar Blue WD2500AAJS 250GB 7200 RPM
LG DVD Burner - Bulk Black SATA Model GH24NS50
GIGABYTE GV-N98TOC-1GI Rev 2.0 GeForce 9800 GT

The BIOS has a lot of option so changing any particular value shouldn't be an issue. Any advice would be appreciated


Thanks in advance