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8. 15. That's the computer's inactivity, by the way, not yours. See the 'Client-side setup' section for this tidbit.
9. MSI. Stands for Microsoft Software Installer; see 'Windows Installer Service' for more.
10. MSIEXEC.EXE. Again, 'Windows Installer Service' has this detail plus a few others you should know.
To really understand how user profiles work (and group policies, for that matter), you should understand at least the most basic basics of the Registry. The Registry is the central store of information that Windows XP and Windows XP programs use to track all the software and hardware on the machine, including details about how that software and hardware are configured.
The Registry isn't the brain of Windows XP, but it's a lot like its spine: that is, where most of the nerve endings come together. And, like your spine, the Registry is vitally important. Windows XP can't even roll out of bed without the clues that Microsoft has tucked away inside the Registry. After startup, Windows XP, and the programs you run with it, use the Registry many thousands of times in a typical computing session - to find necessary files, recall user preferences, enforce security restrictions, and perform hundreds of other actions.
If something goes wrong with your Registry, you may not be able to use your computer until you fix it. If something goes wrong with a program you're running, or with Windows XP itself, you may need to use the Registry to repair it. If a hacker knows more about the Registry than you do, you could be at risk for some of the more insidious viruses around, like the 'I Love You' bug that kissed tens of millions of PCs in May 2000.
Microsoft is moving away from the concept of having the Registry contain every possible configuration setting. Windows 2002 and 2000 Server use a separate database, Active Directory, which maintains information about how the network is organized. Most of the low-level details about network nuts and bolts remain in the Registry, though.
The Windows XP Registry shares many similarities with NT 4.0, which incidentally is why the upgrade path from NT 4.0 or Windows 2000 is much smoother than from Windows Me or 98.
The exam is sure to include one or two questions about the Registry. Also be aware that you'll spend more time mucking about with the Registry in the real world than the exam leads you to believe.
The Registry appears as a single, unified database when you view it with the new, unified Registry Editor (REGEDIT.EXE), but it doesn't reside in a single file on disk. Most of the Registry's several files live in C:\WINDOWS\ SYSTEM32\CONFIG, but some live in the profile folders under C:\Documents and Settings.
Why not just have one big meaty file with everything in it? Although the 'one monster file' design has a certain aesthetic appeal, a few very good reasons exist for separating the Registry into multiple files:
* Different users can create and see different user-specific settings (NTUSER.DAT, USRCLASS.DAT) based on their logon names, but all users on a machine can share the same machine-specific settings.
* On a network, the user-specific settings (NTUSER.DAT, USRCLASS.DAT) can live on a network server and 'follow a user around' as he or she logs onto different machines.
* You can maintain a separate group of default settings (the NTUSER.DAT that lives in the Default User profile folder) for any new user who logs on, while keeping every existing users' settings intact.
* The security-related parts of the Registry (SECURITY and SAM) can be restricted from view and protected against modification.
* The machine-specific parts of the Registry (HARDWARE, SOFTWARE, SYSTEM) stay with the machine.
* If something goes haywire, you may be able to restore part of the Registry from an earlier backup, instead of restoring all of it. The benefit of such a 'surgical restore' is that you may lose less work.
When you view or edit the Registry with REGEDIT.EXE, you see a hierarchical database structure in the left window pane, as shown in Figure 12-1. This structure expands before your eyes when you click the little plus signs, just as a directory tree does in Windows Explorer. Also, as in Explorer, the right window pane displays the contents of whatever item you highlight in the left pane.
Figure 12-1: Primary Registry branches, or 'root keys.'
The five so-called root keys are the top-level organizational structures in the Registry. The display in Figure 12-1 is a little misleading in that of the five root keys, three are aliases, or pointers, to subkeys of the two 'real' root keys.
For example, HKEY_CURRENT_USER (abbreviated HKCU) contains all the user-specific Registry settings for the currently logged-on user. Saying (and writing) HKCU is easier than figuring out the current user's Security ID and specifying a key such as HKU\S-1-5-21-448539723-842925246-2089417427-500 (where HKU is short for HKEY_USERS). Also, Windows 9x programs don't know about Security IDs, and therefore need to see HKCU to run under Windows XP.