Normally you won't need to disable a device unless you're troubleshooting. But if you do, it's a simple matter of right-clicking the device and selecting Disable. Devices that have been disabled for any reason can be restored by right-clicking and selecting Enable. Normally, the enabling and disabling of devices doesn't affect the operation of Windows and doesn't require a restart but if you disable a vital component such as the display adapter, your computer will close down and restart automatically.

Any computer built within the past 10 years or so uses Plug and Play technology, which means that hardware can be added or removed without having to go through any special installation or removal procedures. Nevertheless, right-clicking an entry in Device Manager reveals an Uninstall option, whose purpose is to completely remove all the driver and Windows Registry entries for the selected device. In situations where a device is malfunctioning and all attempts to revive it have failed, choosing the Uninstall option and then rebooting can sometimes do the trick¬when the computer restarts it thinks the device has been newly added, reassigns resources to it and then looks for an appropriate driver to get it working .

If a device is installed but is not working correctly, and therefore is flagged with an exclamation mark, the first line of approach is to double-click the item's entry in Device Manager to display its Properties dialogue box. On the General tab is a panel labelled Device status, which contains an error code, a plain English message describing the problem and a suggested solution. In nearly every case the problem is with the driver, and clicking the Reinstall Driver button launches the New Hardware Wizard to guide you through the process of installing one.

If you suspect that a fault has been caused by a recently updated driver, don't use the Reinstall Driver button. Instead, click the Driver tab and use the Roll Back Driver button to reinstate the old driver. In general, it's a good idea to use the most up-to-date drivers, but some recently released versions might contain bugs, so the roll-back facility can be a life-saver.

In the worst cases, installing a new driver that's unsuitable or flawed can cause a computer to display a blue-screen error and fail to load Windows. In such cases, tap the F8 key while the computer is starting up and choose to use Safe Mode (or Safe Mode with Networking if you have an internet connection). This is a minimal troubleshooting mode that enables you to fix problems that are preventing Windows from starting normally, while networking-enabled mode allows you to search for help and new drivers on the web. Once in Safe Mode, use the Roll Back Driver function to fix the problem and then reboot as usual.