What is the FSB speed of your processor? If your mobo is a 266 then your processor is a 266, or lower.
You seem to be trying to run the ram too fast for the cpu fsb.
My pc mobo has a max ram speed of 333, my cpu is a 2400 xp athlon, with a fsb of 266. My ram is 266 max so my bios settings are 133, the ram is ddr so it runs at 266.
The cpu, mobo & the ram must be all capable of running at the same higher speeds for any upgrade to succeed.
