1. A particular model year wouldn't be available until after that year, instead of before.

 2. Every time they repainted the lines on the road, you'd have to buy a new car.

 3. Occasionally your car would just die for no reason, you'd have to restart it, and, for some strange reason, you would just accept this.

 4. You could only have one person at a time in your car, unless you bought a car '95 or a car NT, but then you'd have to buy more seats.

 5. You would be constantly pressured to upgrade your car. Wait a sec, it's that way NOW!

 6. Sun Motorsystems would make a car that was solar powered, twice as reliable, 5 times as fast, but only ran on 5% of the roads.

 7. The oil, alternator, gas, and temperature warning lights would be replaced with a single "General Car Fault" warning light.

 8. People would get excited about the "new" features in Microsoft cars, forgetting completely that they had been available in other brands for years.

 9. We'd all have to switch to Microsoft Gas (tm).

10. Ford, General Motors and Chrysler would all be complaining because Microsoft was putting a radio (probably an A.M. radio at that) in all its models.

More Ways Things Would Be Different if Microsoft Built Cars:

1.  Your new car would come in a package four times its own size.
 
2.  The first time you start your car, it will not go in reverse, the wipers don't work and the turn signal only goes to the left.  The vehicle only becomes fully functional after you spend 3 to 4 hours giving it a tune-up, ably assisted over the phone by an engineer in Mobile, Alabama who has actually never worked on your model and can't access the owner's manual right now.
 
3.  The owner's manual would cost extra and appear to be written in Esperanto.  Alternatively, there would be no manual.  The car itself would answer all your questions and help you fix all the problems but only if you already knew the answer and the car wasn't experiencing the particular problem.
 
4.  If you got a flat, you'd have to replace all four tires because new tires are not compatible with the ones that came with your car, no matter how recently you bought it.

5.  If you lost your keys, you would have to ship the entire car to Redmond, Washington in order to get the door open.
 
6.  The day after you bought your car at full price, you'd see it advertised in the paper, being sold in a package deal with a pick-up truck and a riding lawn mower, for less money than you paid.
 
7.  The car alarm would only work on people previously known to it.