Remove the 2x1Gb memory modules while overclocking.
Mixing memory brands can make it more difficult to get a stable overclock.
Once you've reached your o/c goal, you can try tweaking for stability with 6GB of memory.
Let us know what specific altered bios settings won't let your system boot.
Before booting into windows, boot using a bootable Memtest86+ usb or optical drive.
Even with good memory, Memtest86+ can often generate errors when some bios settings aren't quite right.
With an unstable o/c, you run the risk of possibly corrupting your o/s boot drive.
We can best help you after you create a detailed hardware list in the PC Specs portion of your
forum profile http://forums.tweaktown.com/profile.php?do=editprofile at the bottom of the
profile page or in your forum signature http://forums.tweaktown.com/profile....=editsignature.
Be sure to include brand names and model numbers.
note: I changed your thread title from Q0400 to Q9400.