Read the sticky in o/c forum:
http://www.tomshardware.com/forum/240001-29-howto-overclock-quads-duals-guide
x38-DS5 is an underrated mobo. Its vdroop is non-existent or minimal. On top of that, the vdimm defaults to v1.925 as opposed to v1.8. So trying each stick of high-voltage ram in each slot to get the board to post may not be necessary. Those are what overclockers are looking for in a mobo.
"CPU Host Clock Control: enabled" unlocks the FSB so you can put anything in FSB.
How many sticks of ram are installed? If 2, vdimm may be ok at stock. If 4, vdimm needs to be higher. +0.30v is a good start.
DDR2 voltage_ normal : see above
PCI-E OverVoltage Control : normal
FSB OverVoltage Control : +0.15v
(G)MCH OverVoltage Control : normal
MCH Reference Voltage Control : Normal
DDR Reference Voltage Control : Normal
DDR Termination Voltage Control : Normal
CPU Voltage Control : 1.25v+
You will need to bump the vcore up to 1.45v gradually. The cpu cooler determines how high the vcore can be. Stock cooler will be very limiting. If you want to be safe, keep it no higher than 1.3625V.
http://processorfinder.intel.com/details.aspx?sSpec=SLAWQ
I don't think it can hit 3.4ghz at that low voltage. Start out from 333mhz fsb and up it by 50mhz. Do memtest 1 pass. If it errors out, bump vcore up & redo memtest.
http://www.memtest.org/#downiso
When you hit the highest stable o/c, boot up windows & do orthos x2 for 8 hours:
http://files.extremeoverclocking.com/file.php?f=200