Ford Repair: 2000 Ford Taurus Drivetrain, wheel bearings, ford taurus

Question
My 2000 Taurus has been driven 40,000 miles and for the past 15,000 a droning noise has been coming from the front end of the vehicle.  At first I thought it was tire noise but when I cross-rotated the tires the noise was the same.  The noise is definitely being made by a rotating component/unit somewhere in the drivetrain and its pitch is speed dependant i.e. the faster I go, the higher the pitch.  Any light that you can shed upon the problem would be greatly appreciated.

Answer
The next thing to rule out are the wheel bearings. Remove the wheels again and check for play in the bearings by torqueing the brake disc this way and that and in and out. If any play at all is detected you need further work/replacement of bearing and or adjustment. If out of adjustment for this long(15K miles) no doubt they will need replacing. Look for grease and oil in places it should not be. This will help zero in on the problem. Also, if play is not detected, rotate the discs and carefully listen or "feel" for grinding. The rotations should be perfectly smooth and silky.