I was fed up of my previous mouse, which would occasionally behave erratically (for example, the cursor would start wandering off to one side of the screen, or it wouldn't move when you moved the mouse).
Inserting new batteries typically fixed that, but only for a while. So I decided to go out and buy a good old wireful mouse. A Microsoft one, since I had heard good things about their hardware.
I finally found one—not the IntelliMouse Explorer I had been looking for (which they only had in Wireless and, I believe, Bluetooth versions, and I didn't want to trust their promises of a six-month battery life) but an IntelliMouse Optical. I kind of wanted to have an optical mouse for a time now anyway :)
I installed the software and shut down the computer. Stella plugged the mouse in; she asked whether there's only one way that the USB plug will fit into the socket and I said yes.
I restarted the computer and—no mouse. (I had taken the batteries out of the other one so that the computer wouldn't be picking up signals from it.)
I navigated to the Mouse control panel using the keyboard and tried a few troubleshooting steps, to no avail.
Next, I crawled behind the computer and saw that Stella had put the USB plug into the Ethernet socket! No wonder the mouse couldn't work. Unfortunately, there aren't any free USB sockets at the back: the four that there are are taken up by the keyboard/mouse wireless receiver, my PocketPC cradle, the scanner, and the printer.
So I plug in the mouse at the front, where there are two more USB sockets behind a cover, just to see whether it works in principle. Hm, still no mouse after rebooting. However, after logging in, Windows recognises the mouse and installs it; a bit later, I can move the cursor by moving the mouse. After a reboot, I can also use the mouse in the login screen.
I deactivated the other mouse in the Mouse control panel. However, I still can't see how to set up the various buttons of the mouse; perhaps that only works if only Microsoft mouses are connected to the computer? But I don't particularly fancy getting a new keyboard.
I think I will be getting a USB hub, though, so that I can plug my mouse in at the back.