Microsoft Download Center

For Microsoft branded hardware (Microsoft doesn't produce any hardware
but merely licenses someone else to stamp "Microsoft" on their
products), I usually start at:

http://www.microsoft.com/hardware

Then I go searching on the type of hardware and drill down to the model.
So, with the info you provided:

- I hovered the mouse pointer over the "Mice and Keyboards" link on the
left panel. This brought up a submenu where I clicked on "Mice".
- In the "Show Me" listbox, I selected "Wireless Technology" and clicked
the Go button.
- I scrolled the page down to where it showed the "Wireless Mobile Mouse
4000". That's the only match on "4000". You didn't say it was a
mobile version but that's all they listed here.
- I clicked on the product link.
- Dead end. Alas, Microsoft wasn't polite in providing links to
software and manuals specifically for this product.
- So I clicked on the "Download Software" link in the left panel.
- Clicked on the "Software for Microsoft keyboard, mouse, and
fingerprint reader products" link.
- Selected the following in the listboxes:
o Type of product: Mouse
o Product: Wireless Mobile Mouse 4000
o Operating system: Windows XP (32-bit). That was a guess versus a
64-bit version.
o Language: English (same as you used in your post here).
- That gave me a link to the Intellipoint 7.1 software.

If you don't need support for the tilt scrolling or extra 2 buttons then
a 3-button scrollwheel mouse driver already included in Windows should
be sufficient to work with this mouse.

As I recall with installation of the Intellipoint software, you are
supposed to select with which product it is to work. If you installed
Intellipoint already, maybe you picked the wrong product during install.