AMD Athlon 2600+ Stop error upon booting with 166Mhz FSB

I am having difficulties booting up into Windows XP when
my Athlon XP 2600+ (333Mhz FSB version) is running at
166Mhz FSB (333).
As soon as windows boots when running my processors
intended speed I recieve a STOP error message and it
reboots 2 seconds later, so i havnt got the chance to
investigate the error codes etc. I have tried several
different FSB/RAM speed combinations that my motherboard
allows but still the same effect unless i run Auto detect
ram speed and 133Mhz CPU FSB.

My hardware is listed below:

Gigabyte GA-7N400 Pro motherboard (nForce2 SPP/MCP-T)
AMD Athlon XP 2600+
512MB Corsair PC2700 (2x256) running in dual channel config
SATA80GB Seagate HDD
Leadtek GeForce4 MX440 (4x AGP)
Antec AMG660 case with 330Watt PSU

Here is what I have done during installation.
1. Disable nForce2 sth bridge stuff (LAN,AC97,IEEE etc)
2. Set processor FSB to 133Mhz, RAM on AUTO instead of SPD
(333Mhz)
3. Install windows XP fresh on an NTFS partiction (8GB)
4. Install nForce2 drivers (everything incl video)
5. Enable Nforce2 sth bridge stuff (except USB2.0)
6. Download from Windows Update (SP1 and security etc)
7. Reboot with SP1 installed (everything works fine at
this point)
8. Change processor FSB to 166Mhz (actual specified speed)
9. Upon reboot i get a stop error.

Any help would be greatly appreciated thank you.

Mark Eisenhut