I just bought a Microsoft Natural Ergonomic Keyboard 4000 and was chuffed to bits on first inspection....then i plugged it in! For some reason every time i start up the computer with the keyboard attached the mouse doesn't work. After navigating through control panel using the keyboard (tedious) i discovered that the computer was no longer aware i had a mouse! Switched off and swapped k/b and everything works fine and the mouse is back in the device manager. Anyone got any insights?

You could look at the web sites for the mouse and keyboard models to see if you can find any t-shooting info that would help, but there may be nothing useful there other than something like the following info. If the mouse and/or keyboard is a "combo" device, that is, it can be used with a PS/2 or USB connection, with one type on the cord and the other type available by plugging in a simple adapter that came with the device, use the simple adapter with one of the devices to connect it to the other type of port, and you should have no problems. e.g. I have a Logitech "combo" mouse that has a USB connector on it's cord but it doesn't work properly and is sometimes not detected when certain other USB devices are connected to the computer - if I use the simple USB (female) to PS/2 (male) adapter that came with the mouse and plug it into the PS/2 mouse port, both the mouse and the USB device it conflicted with work fine. If neither device is a "combo" device, there may be nothing you can do. The cheapest option is to get a "combo" USB/PS/2 mouse and use the other type of connection from what your present mouse uses, or get a mouse connected by only PS/2 or USB, whatever type is not the same as what the keyboard uses, or to use a "combo" serial/PS/2 mouse or a serial only mouse rather than a USB or PS/2 connected one, and use the serial connection, if you have a free physical Com port and a free IRQ the mouse can use.