I found your post here and decided to register as a member to give you the following answer:
There is no way you can overclock a xw4400..... unless:
You change your processor to a QX6700 that has an unlocked multiplier (check ebay.. 60 dollars should do it) and then download a program called Throttlestop 5.00, run it and adjust the multiplier after you pressed the UNLK button. After you found a stable overclock, make it autostart at startup and you're good to go.
I did the same with mine and running now 3,2GHz stable (multiplier 12x) with the BIG stock cooler (that tower inside
) at 100% load a core temp of 83C*
It is possible to adjust the VID (I believe that is Vcore) to your need, but keep an eye on the temp. I did not mod the cooler so did not make a bigger OC but you should be able to get up to 3,45GHz (13X266) with a higher VID, TDP will go to 250W!!! Make sure you set the VID higher FIRST...when you try 13x...otherwise the system crashes and reboots, then it will hang at loading the OS, do a system last known good configuration ....
You will find it impossible to overclock the FSB and to my knowledge, nobody ever made a Bios for this motherboard "Hewett-Packard 0A68h" to unlock the FSB.
I believe the max FSB of this motherboard is 1066MHz (4x266) and that is your limit.
If you do not have an unlocked processor but one that runs on a lower FSB, for example 800MHz (4x200) you can do a Hardware mod to get it on a 1066MHz FSB (BSEL mod) search for LGA775 BSEL mod with whatever search engine you prefer.
Thats my 20 cents....
Good luck
But I have been proven wrong before so don't take my word for it.... just what I found until now on the web.
XW4400 supported processors:
QX6700 processor / 2.66 GHz, 4 MB x 2, 1066 FSB
Core 2 Duo E6700 Processor/ 2.67 GHz, 4 MB L2, 1066 MHz FSB
Core 2 Duo E6600 Processor/ 2.40 GHz, 4 MB L2, 1066 MHz FSB
Core 2 Duo E6420 Processor/ 2.13 GHz, 4 MB L2, 1066 MHz FSB
Core 2 Duo E6320 Processor/ 1.86 GHz, 4 MB L2, 1066 MHz FSB
Core 2 Duo E6300 Processor/ 1.86 GHz, 2 MB L2, 1066 MHz FSB
Core 2 Duo E4300 Processor/ 1.80 GHz, 2 MB L2, 800 MHz FSB
Core 2 Duo E2160 Processor/ 1.80 GHz, 1 MB L2, 800 MHz FSB