Micky wrote:

MS Wireless mouse 4000

Window XP Pro.

All but two function work.
Not working is the side and scroll buttons.

I went in to Control Panel Mouse and it says it cannot find a Microsoft
Mouse so there is no way now to get these two needed buttons to work.

How do I get it all working ?

If I need to download something, please provide details.

Went to https://www.microsoft.com/accessories/en-us.
Clicked on "Mice".
Clicked on "Learn more" (or the mouse picture) for the "Wireless Mobile
Mouse 4000".
Clicked on "Downloads".
Under the "Software & Drivers" listbox, Windows 7 is listed (for 32-bit
and 64-bit).
You never identified the bitwidth of your OS. Once you pick a bitwidth
for the OS, the software link changes to match. In this test, I picked
"Windows 7 (32-bit only)".
The software link changed to "Windows 7 (64-bit only), Mouse and
Keyboard Center 11". Clicking will download a
MouseKeyboardCenter_64bit_ENG_12.181.exe, 45.9MB.

So, have you actually retrieved the software needed to define the extra
features of that mouse beyond a generic HID (Human Interface Device)?
This device did not come with software media to install the necessary
ancilliary software beyond just the reference software that comes
bundled in Windows? Did you even search before posting, or was this a
knee-jerk inquiry?

You also find the Quick Start manual there. Presumably you also don't
have that manual since since it gives the URL from which you obtain the
software downloads for Microsoft's hardware. Often software is media no
longer bundled with hardware (and for software required to define the
hardware beyond a generic device). It should have come with a tiny
booklet (the manual is very short) that mentions where you download the
software, or it might've been printed on the packaging.