Reviving this thread because I have the same problem.
I have installed a xeon X5450, SLBBE, E0 stepping, cpuid=1067a, in a HP 3120 SFF box, pegatron APIEL-LA3 mobo, intel G43 chipset. CPU runs ok, win 7 installed ok, but the fan is going full blast all the time, doesn't idle (a core-2 quad Q8300 I tried however was fine).
The bios is AMI - not the same one as the OP, sp50660.exe ver 6.07. This comes in an exe package containing UCORESYS.SYS, UCOREVXD, UCOREW64.SYS, afuwin.exe, a .cva file, flash.bat and a vxd file as well as the main bios file EU36.07. I extracted the exe using 7-zip to add this cpuid = 1067a microcode
cpu0001067a_plat00000044_ver00000a0b_date20100928.bin
(I also updated the 775 core-2 microcode) to the main bios file EU36.07, which I had to temporarily rename to .rom, using mmtool (following the tutorial on delidded.com).
I then created a DOS bootable usb drive using RUFUS, put on the modded bios and AMI flash tool AFUDOS.exe. Although this PC's BIOS setup doesn’t have usb listed as a boot device, in practice once the usb is plugged in it is detected and pressing ESC on boot goes to a boot choice recovery screen where the USB is listed.
The command
AFUDOS.exe /p /b /c /n /x
(see:
http://www.ecs.com.tw/extra/flashutl/afuusb.pdf )
then flashed the bios successfully.
Reboot success into windows 7. Fan nice and quiet! Things seemed a bit slow initially, however CPU-Z reported the cpu running correctly at 3GHz, and a test using adobe DNG converter gave same results as before for conversion of a folder full of pics – 9 secs.
Date however had reverted to 2002.
So it's looking like I have had more success than the OP. What else should I check...??