I NEVER use any Driver software that comes with mice. But that's just me.
Generally, the built-in generic mouse driver supports any number of buttons and scroll wheel axes; the default behaviour for the mouse driver is to send any number of well documented system messages for the various scrolling features of the mouse; in the case og horizontal "tilt" scrolling, the active window is sent WM_MOUSEHWHEEL messages.
Now, this might follow with a question such as "why is their mouse software to begin with" Well, that's pretty simple; the generic Windows-included driver can't possibly include everything, and the older versions included with older versions of windows didn't support many things; Windows 98 and earlier, for example and NT4, don't, by default, support any number of these messages- this includes those for any "wheel" messages.
Thing is, the "driver" software, as we all know, has essentially full control over what the mouse actually ends up doing; with windows 98SE for example, using a scroll-wheel mouse often requires to use of the included drivers, and the drivers themselves say "ahh, I'm running on a version that doesn't support the mouse wheel; I'll emulate it's functionality using different messages" and usually it ends up sending WM_VSCROLL and WM_HSCROLL messages; this is why you often see options for "how many lines" to scroll at a time.
Additionally, many drivers (such as the Intellipoint) will send their own "custom" message to the active window when the scroll whell or extra features of the mouse are used; if the program responds to that message with TRUE (meaning "yes, I have responded and acted on that message" the driver generally says "alright, cool, no need for me to hack about with you and send you scroll messages instead" otherwise, (if the active window ignores the message) the driver sighs and "emulates" the wheel actions using the messages for window scrolling. In general, it works well.
What this means however is of course that each application can do what they please for each message; but in some cases what happens is "generic" (when you get the H/VSCROLL messages instead) I believe this model was brought forward for compatibility; that is, Win7 still sends the various scroll messages if an application doesn't respond to the wheel messages.
When we speak of "programmable" mice, it's actually a misnomer; when you change the settings in a mouse control panel for what the tilt or scroll features do, you aren't programming how the mouse itself responds insomuch as you are programming what the driver tells your applications the mouse does for each feature; for example, if you enable the swap mouse buttons feature, windows itself will swap the various button messages to switch the parameters so left clicks are interpreted as right clicks; in the same fashion, "programming" the scroll and tilt wheel functions simply tells the driver what to send to the active window. In the case of Copy and Paste, for example, it's as simple as sending a WM_COPY or WM_PASTE message rather then the specific wheel scroll messages. (or the even more default window scroll messages).
