How long does it take to travel by car from Vienna to Salzburg? How many kilometers?

A good place to find information on car travel is http://www.viamichelin.com which I find to be fairly accurate.
by train:
317 km
travel time
for the hourly trains departing at :20 2h 39m
for the hourly trains departing at :44 3h 5m
EUR 47,50 for 1 person 2nd class (EUR 80,80 for 2 persons).
The new Railjet trains used on this route (but not for all connections) are really nice.
http://en.wikipedia.org/wiki/Railjet
http://railjet.oebb.at/#/economy/

If you are travelling by car, be aware that you have to buy a "Vignette" before using the motorway. There are high fines.
If you have sufficient funds to rent a Ferrari, oops better a supersonic fighter jet, you'll be there in no time.
Naturally, you can litigate me, if some other jerk caused an accident on the motorway or even crashed a plane at Salzburg airport.
So if you fly, don't forget to take a parachute with you. At least you'll be able to land.