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Fixes for three of the most common Windows glitches

Cures for an update gone bad, a trashed Registry, and a shutdown failure.

Windows breaks; it's a fact. Sometimes the only fix you need is a system restart, but other times you may feel like you'll never get your PC working again. While not even a building full of Microsoft engineers can promise solutions to every Windows problem, these tips will help you begin your quest for a cure.

Windows won't update
First, make sure you're logged into an administrator account. Next, open the Windows Update log, which is at C:\Windows\Windows Update.log, and look for an error message, which may include an error code you can search for in Microsoft's knowledge bases. (Make sure you have Windows set to show hidden files: Open Windows Explorer, and in XP, click Tools>Folder Options>View>Show hidden files and folders; in Vista, click Organize>Folder and Search Options>View>Show hidden files and folders.)

Windows Update log
Scan your Windows Update log file for clues to your system's update failures.

Now visit the Windows Update Troubleshooter and browse around for an entry relating to the error. If nothing on this page solves the problem, try disabling your antivirus and anti-spyware programs, your firewall, and any Web accelerators you've installed before going to the Windows Update page. Just be sure to reactivate your security programs before you browse anywhere else.

If you're still unable to update Windows, here are three more things you can try:
Check your clock to make sure your PC is set to the correct time and date. Double-click the time in the bottom-right corner of the screen to open the Date and Time Properties dialog box (in Vista, click Change date and time settings).
Log into another administrator account and try to update. If you don't have two administrator accounts, open the User Accounts Control Panel applet, click Create a new account (in Vista, select Manage Another Account first), and step through the wizard, choosing Computer administrator as the account type (Administrator in Vista).
Start Windows in Safe Mode and retry the update. To enter Safe Mode, press F8 after your PC starts but before Windows loads, and choose Safe Mode from the resulting menu.
You'll find more update-troubleshooting options on's Windows Update Checklist.

The Registry has gone haywire
The fastest and simplest way to repair a garbled Registry is via Windows' System Restore: In XP, click Start>All Programs>Accessories>System Tools>System Restore>Restore my computer to an earlier time (likely selected by default)>Next. Choose a restore point on the calendar, and step through the wizard. In Vista, press the Windows key, type "system restore," and press Enter. Vista recommends a restore point; if you approve, click Next>Finish. Otherwise, click Choose a different restore point>Next, make your selection, and step through the wizard.

Windows Vista System Restore dialog box
Vista's System Restore applet chooses a restore point for you, or you can opt to select another.

You always have to be careful when you make changes to the Registry, which is why you should triple-check any Registry-cleaning utilities before you use them. One that has been around for a while is TweakNow's RegCleaner Standard (the company also offers a $27 Professional version).

Windows doesn't know when to quit
Sometimes Windows reboots when you only want it to turn off. This may be caused by the OS thinking a shutdown is actually a crash, which it is programmed to respond to by restarting. To disable this feature, right-click My Computer (Computer in Vista), choose Properties>Advanced (Properties>Advanced system settings>Advanced in Vista), and click Settings under Startup and Recovery. Uncheck Automatically restart under System failure, and click OK.

Windows' Startup and Recovery Settings dialog box.
Stop Windows from restarting automatically after a crash by unchecking Automatically restart in the Startup and Recovery Settings dialog box.

This doesn't address the cause of the "crashes", however. A primary reason for such failures is a hardware or software conflict, so if you've recently installed some device or program, check the vendor's Web site for updated firmware or a new driver (more on fixing hardware conflicts tomorrow).

If your shutdowns are just slow, Windows may be clearing your virtual memory and system-hibernation cache (sleep mode in Vista) when it closes, which adds considerably to the shutdown process. To reset this option, click Start>Run (in Vista, simply press the Windows key), type gpedit.msc, and press Enter to open the Group Policy Editor. Navigate in the left pane to Computer Configuration>Windows Settings>Security Settings>Local Policies>Security Options, double-click Shutdown: Clear virtual memory pagefile, choose Disabled (if it isn't selected already), and click OK.

Tomorrow: Remedies for Windows networking and hardware failures.