I live in Oslo, Norway, and I commute by bike all year round. As others here have pointed out, studded tyres are the best way to ride through the winter. It feels like riding on gravel road, and you have to take similar precautions. The tyres that are recommended here, Nokian and Schwalbe, are probably the heavy duty ones with 298/304 studs. There are some lighter city-slick type tyres with fewer studs that rolls easier. They could be considered if you are in an area with more ice than snow on the streets, typically in a winter climate where the temperature is just around freezing point, and where the downpour is more likely to be rain (that later freezes over) than snow. As soon as you get heavier snowfalls, the rougher tyres are the only way to go. They'll give you heavy friction on tarmac, though.
Also take into consideration that the heavy salting on the roads in wintertime is taking its toll on your bike. That also goes for the fine gravel and dust that mixes with snow. The massive quantities of sludge in city streets will splash itself plentifully all over your bike, and corrode and grind all delicate moving parts as well as brake shoes and rims. This shortens the life-span of the particular parts and the bike as a whole considerably. My solution to this is two-fold: First, use your old "been-in-the-garage-for-15-years" bike as a winter bike, equipped with cheap new parts if necessary, and of course studded tyres. Or you can or buy a cheap bike from the store. Do not use your beloved expensive state-of-the-art bicycle. Second, rinse the chain, derailleur and rims/brakeshoes after each trip. I fill up a 10-liter bucket with hot water and pour it over the parts every afternoon when I come home. This minimizes the the wearing. The morning after, I lubricate the chain with oil for wet condtions (ask your dealer), every day. Keep the bike indoors, otherwise you'll get problems with frozen parts.
Also, pay special attention to the brake shoes. They will wear away in no time, and you do not want to hear the ugly sound of metal brackets grinding your rims while going downhills at full speed. Expect to change brake shoes a couple of times every season. Happy riding!