He's talking about his mouse wheel, not his mouse sensitivity. They're two different things.
What kind of programs are you noticing this in? Something like browsing the Internet with your browser? In your Control Panel, you should have a Mouse icon. There should be a wheel tab there, and you can change the number of lines of text that the mouse will scroll when you move the mouse wheel.
If that's not what you mean, then I dunno. Maybe its batteries are dying?