Try here

http://www.google.co.uk/search?hl=en&q=how+a+mouse+works&btnG=Google+Search&meta=

Start/Control Panel/Mouse then look at the Buttons tab and the Scrolling
tabs. This will show you your mouse's current settings and options.

JS

From the Intellimouse Help Files:

[quote]

Wheel button AutoScroll
Use the wheel like a button (press and release it) to automatically move
around in a document, without rolling the wheel or clicking the scroll bar.

Additional Information about using the wheel  AutoScrolling  Some
programs (such as Internet Explorer and Microsoft Excel) provide
AutoScrolling functionality that allows you to scroll through a document
automatically.

To AutoScroll, press the wheel button and observe the position of the
origin mark that appears on the screen. Move the pointer in the
direction that you want to scroll. The further you move the pointer away
from the origin mark, the faster the document scrolls.

To quit AutoScrolling, simply click a pointing device button or press a
key on the keyboard.

Panning  Some programs (such as Microsoft Word and Microsoft Excel)
provide panning functionality that allows you to scroll through a
document automatically. Panning is similar to AutoScrolling, except you
must press and hold the wheel button.

To pan, press and hold down the wheel button and observe the position of
the origin mark that appears on the screen. While holding down the wheel
button, move the pointer in the direction that you want to pan. The
further you move the pointer away from the origin mark, the faster the
document pans.

To quit panning, simply click a pointing device button or press a key on
the keyboard.

[end quote]

It's application specific, some programs make use of the wheel button,
others ignore it completely.  In the ACDSee image viewer for example you
can use it to togle to full scree view, try it in different porgrams and
see what it does.

John

It's your choice. Go to Control Panel | Mouse, see how it's set now, and
change it as you prefer.

Norman,

If you are going to use newsgroups lie this you need to get you email
address out of your settings.
Spammer harvest email address's from these sites all the time.

allows the page (like a web page) to 'auto scroll'.  Read the documentation
for the mouse, for the specific functionality.