If you want to stop the smooth scrolling of the task bar you need to click on start | settings | folder options.
On the dialog box that opens, find the visual settings section.
You need to remove the check marks from smooth edges of screen fonts and from show window contents while dragging.
Click OK or Apply.
If they are already unchecked you need to check them, click Apply and then uncheck them and click OK or Apply.
After doing this you can go back and check the smooth edges of screen fonts option if desired.
To get the smooth scrolling you need to check the show window contents while dragging.