I don't think you can damage motherboards as easily these days - they just won't boot. But, I agree that you should be able to get past 266 - you can probably hit low 300s at least with that board and cpu. Don't be afraid to go up to 1.45 with this chip.
I built almost similar system before and got to 3.5ghz w/o much effort (I believe I used a gigabyte p35 tho...) --
I'd recommend higher fsb and lower multi if you find a speed you want to stick to. my experience, lower mutlis seem to be more stable - but you'll need a really fast mobo.