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* SIGVERIF.EXE, the Signature Verification tool, lets you quickly scan protected system files and verify that their digital signatures are intact. This utility produces a log file, SIGVERIF.TXT, showing the version, modification date, and signed-or-unsigned status of each file. Using the utility's advanced settings dialog box, you can set the program to scan non-system files in any location you specify.
* SFC.EXE, the System File Checker, also lets you check the digital signature of system protected files. It works from a script, batch file, or command prompt. SFC doesn't show you the file details that SIGVERIF does, and it doesn't let you scan non-system files. However, SFC does two things that SIGVERIF doesn't: It repopulates the DLLCACHE folder if it detects system files added since Windows was installed, and it offers to replace any system files that it determines are missing or different from their original versions.
Instant Answer The key parameters for SFC.EXE are as follows:
* /CACHESIZE lets you specify the maximum size of the DLL cache.
* /PURGECACHE clears the DLL cache, and then repopulates it.
* /SCANNOW initiates an immediate scan of system protected files.
* /SCANONCE sets SFC to perform a scan at the next reboot.
* /SCANBOOT sets SFC to perform a scan at every reboot.
* /REVERT returns the scan setting to the default.
Windows XP Recovery Methods
In times of serious trouble, when you can't even get Windows XP Professional to start properly, you're looking at performing some system recovery. Windows XP offers various degrees of recovery, and this section treats them in the same order I usually recommend trying them: from least destructive (Last Known Good boot) to most destructive (Automated System Recovery).
Last Known Good boot
When you log on successfully to Windows XP Professional, the operating system assumes a 'good' boot and writes the control set information to the Registry as the 'Last Known Good' control set. (Remember, a control set is a collection of device drivers and their settings.)
Later, if you add a device that interferes with Windows' ability to start normally, you can apply the Last Known Good boot technique, as described in Lab 15-2. Windows XP takes the 'LKG' process a bit further than Windows 2000 does by rolling back device drivers to their state at the last known good boot, not just the Registry control set information.
Lab 15-2: Using the Last Known Good Configuration
1. Restart the system after the failed boot by pressing F8 at the 'Starting Windows' text mode prompt.
You can also boot while holding down the Ctrl key, if you're worried about tapping the F8 key quickly enough.
2. At the text mode boot menu, choose Last Known Good Configuration (Your Most Recent Settings That Worked).
Doing so instructs Windows to use the last known good control set instead of the current, or default, control set. Because the last known good control set doesn't call the new device driver, it should let you boot normally.
Warning If you suspect a device problem, restart the computer, and forget to choose Last Known Good Configuration, don't log on. The moment you do, the current control set becomes the Last Known Good control set, and you'll have to figure out some other way to exorcise the evil device driver.
Tip Now that Windows XP lets you 'roll back' a single device driver via the Roll Back Driver button on the Driver tab of the device's property sheet, you may save time by trying that route instead of Last Known Good, unless you've upgraded multiple device drivers at the same time.
Windows 9x offers a Safe Mode boot option that doesn't activate the Registry and that loads only a minimal set of device drivers (basic VGA, mouse, keyboard, disk). Safe Mode also disables startup programs and 'nonessential' operating system services. Safe Mode has been a boon to troubleshooters, and its absence in NT 4.0 prompted a great deal of pressure from corporate customers for Microsoft to implement something similar in its next operating system.
Warning Depending on your PC's BIOS, USB mice and keyboards may not be available in a Safe Mode boot!
As a result, Windows XP also offers a Safe Mode boot option (press the F8 key at the text-mode boot menu and select Safe Mode, Safe Mode Command Prompt, or Safe Mode with Networking), but it differs from the Windows 9x Safe Mode in some key ways. The most important distinction is that Windows XP Safe Mode activates the Registry, meaning that you can't back up or restore the Registry by using file copy commands in Windows XP Safe Mode.
Instant Answer When you're running in Safe Mode, the words 'Safe Mode' appear in all four corners of your display. Windows XP doesn't load network software in the basic Safe Mode, nor does it load any system services beyond the bare necessities. If you need network access, you can choose Safe Mode with Networking, which allows processing of network logon, logon scripts, and Group Policy settings. The Safe Mode with Command Prompt option starts Windows XP with the command-line user interface instead of the graphical user interface.