Interesting thread. I'm very surprised at the number of people recommending turning off traction control and / or other electronic aids. Frankly, if they're no use on ice, then I'm not sure what they're doing there!
My wife's Nissan X-Trail is brillant in snow and ice. It's a 4x4 but it doesn't have diff locks. It uses its traction control to gently apply the brake to the spinning wheel - thereby forcing the other wheel on that axle to turn. And it does so with spectacular success! The idea that it would apply both brakes is somewhat bizarre - that would, of course, give no benefit whatsoever. I know that many cars' systems will close the throttle a bit or reduce power output in some other way before they start using the brakes to intervene but either way, I find it works very well in the snow. The Electronic Stability Control also works in "loss of control" situations in snow or on ice (e.g. when I boot it half way through a bend, the back end steps out and then the ESC intervenes to spoil my fun)!
I also thought it odd that people think rear wheel drive cars ought to be worse than FWD in snow when it comes to traction - as the main reason all powerful cars have always tended to be RWD is precisely because they CAN'T put their power down adequately through the front wheels?
Lastly, I wonder whether the poor performance of many more powerful modern vehicles on slippy stuff is partly down to their power and torque? As a kid I had very low powered cars (with skinny tyres) and didn't seem to have half so much trouble. These days I have the use of a company diesel MPV which is utterly useless on snow and ice. It weighs 2 tonnes, drives the front wheels through an open diff, and is mapped such that it has virtually no torque below about 1500 revs (in fact it's surprisingly easy to stall) but as soon as it hits 1500, it has MASSES of torque and just lights up its front tyres (often in the wet, never mind snow)!
