As you use Windows, the way it operates is governed by a group of settings that are collectively known as the system state. These settings include the Registry and the files needed for system startup. The system state can be backed up.

The Registry is the configuration file set that controls every aspect of Windows, from which display resolution is chosen, to which programs are installed, to which hardware drivers are enabled. The Registry is absolutely critical -- Windows will not run without it. When you make any changes in Windows, such as installing or removing software or changing settings in the Control Panel, those settings are stored in the Registry.

It's important to understand that the system state doesn't contain any data. Data backup is a separate activity. Some people do not bother with backing up the system state, because they figure they can always reinstall Windows later if needed.

There are several ways to back up the system state. You can:

• Save a backup copy of the Registry through the Regedit (Registry Editor) utility.
• Save a backup copy of the Registry through System Restore.
• Save the system state (including the Registry) through the Backup utility.

These methods are covered briefly in the following sections.

Backing Up the Registry with Regedit

It's a good idea not to make any changes in Regedit because it edits the Registry directly, and this can be a dangerous proposition. One false move and Windows will be disabled entirely. However, in this case, you're not making any changes -- just a backup.

Here's how to back up the Registry with Regedit:

1. Select Start > Run. Type regedit, and then click OK. The Registry Editor window appears.
2. Select File > Export. The Export Registry File dialog box appears, as shown in Figure 1-2.

Figure 1-2: Export Registry File dialog box.

Enlarge image

3. In the Export Range area, select the All option button.
4. Select a save location. If you have a remote location available, such as a network drive, save it there; it won't do you much good to save a backup on your same hard disk as Windows is installed.
5. Type a name for the backup file. (It's good to use a date in the name, such as Registry0604 for a backup created in June, 2004.)
6. Click OK. The Registry is backed up.
7. Close the Registry Editor window.

You might need to restore this backup if something happens that corrupts your Registry file, such as installing bad software or making changes to the Registry that result in Windows not working correctly. To restore a backup, you simply open the Registry Editor and select File > Import, and then select the saved backup in the dialog box that appears.

When you go back to a previous configuration, you don't lose any data files, but Windows loses its recollection of any programs that were installed since that backup. Suppose, for example, you make a backup of the Registry in the morning, and then you install Microsoft Word and create a Word document. After that, you install a game that causes problems, so you decide to restore your Registry backup. After doing so, Word no longer works because it's no longer installed (that is, its entries are no longer in the Registry), but the Word document you created is still there on your hard disk. You now need to reinstall Word.