Windows XP includes a command called Shutdown that does much more than its name might suggest. Yes, you can use it to create a shortcut that you can then double-click to turn off your computer instantly. Just create a new shortcut and include this command in it, exactly as typed:

shutdown -s -t 00

The -s switch means “shut down” (you could use -r to shut down and restart). The -t switch defines a waiting time, measured in seconds.

You can also use the command to do other tasks, such as logging off the current user (use the -l switch), or restarting a remote computer on your network (with the -m switch followed by \computername) . Using the -i switch, you can show a graphical user interface (normally, this is a text-based command). You can include the shutdown command as the last line of a batch file or script to restart a computer after performing a maintenance task.

To see the full syntax for the Shutdown command, open a Command Prompt window (Start, Run, type cmd and click OK) and type the command shutdown without any additional switches or arguments.

On the Windows XP Inside Out forums, a visitor asked: Does anybody know if there are any problems with allowing exceptions in Windows firewall for uPnP?

UPnP is the Universal Plug and Play service. It’s useful and perfectly safe. There was a security problem with UPnP that was discovered several weeks after Windows XP was released, nearly four years ago. That problem was patched in December 2001, and since then there have been no reported security issues with UPnP.

In addition, Windows Firewall only allows traffic on the UPnP ports from your local subnet, not from the Internet at large.

Unfortunately, way back in 2001 several widely read security sites, including the FBI’s National Infrastructure Protection Center (NIPC), posted advisories that recommended disabling UPnP. (The FBI changed that advice within a few days after the Windows XP update was released.) One widely read site even created a tool that disables the UPnP service automatically; that tool is still available for download and I continue to see people advising that it be used. That’s a mistake. The information in those advisories is no longer accurate and that tool is no longer needed.

You should enable UPnP with confidence. It is used by routers and by media sharing devices and home automation products, to name just a few categories of hardware and software.

Look at the top of the Start menu in Windows XP. See the picture to the left of your user name? It was assigned by default when you set up your user account. (You won’t see a picture here if you use the Classic Start menu instead of the Windows XP-style Start menu or if you’re attached to a Windows domain.)

That same picture appears on the Welcome screen, where you log on to your user account. You probably have a frog, or a rubber duck, or a palm tree or a cat as your picture. But did you know you can change this picture? Did you know you’re not stuck with the lame set of sample images that come with Windows XP? Here’s how to personalize the image attached to your logon.

To change the picture used for your account, click Start, and then click the picture at the top of the Start menu. (This shortcut opens the User Accounts Control Panel and is a good one to remember; if you wanted to change something else about your account, you could click the Back button to see other settings.)

Click Browse for more pictures and find an image file you’d like to attach to your account. When you click Open, Windows copies your image to the folder where it stores user photos: %allusersprofile%\Application Data\Microsoft\User Account Pictures. The original image remains intact and unchanged. The copy is resized so that it is 48 pixels wide or high, and saved in Bitmap format, using your user name as the file name. I recommend that you start with a square image; if you use a rectangular image, the width or height will be reduced to maintain the image proportions.

System Restore is one of the most important – and most misunderstood – features in Windows XP. Used properly, it can save you hours of painful reconfiguration if you inadvertently install a bad driver or program. If you don’t understand its inner workings, you’re at a serious disadvantage. Carl Siechert, Craig Stinson, and I spent a lot of time delving into this feature in Windows XP Inside Out, Second Edition and Windows XP Inside Out Deluxe, Second Edition. In Chapter 2, “Installing and Configuring Windows XP,” we explain how you can customize System Restore to match your preferences. In “Recovering After a Computer Crash” (Chapter 39 in the Deluxe Edition, Chapter 32 in the regular edition), we explain how this feature works and how to use it properly.

System Restore settings and preferences are stored in the registry. Most of the values found here can be adjusted safely and easily using the System Restore tab of the System Properties dialog box. By default, System Restore is configured to allow its files to occupy up to 12 percent of available disk space on every drive. On a 60 GB drive, that adds up to more than 7 GB of storage space. That’s excessive. To rein in space usage for a specific drive, open Control Panel, double-click the System icon (it’s in the Performance and Maintenance category if you’re set up to use the Category view of Control Panel), and click the System Restore tab.

From the list of available drives, click the drive letter that corresponds to the drive on which Windows is installed. (Normally, this is C:) Then click Settings to open the dialog box shown here.

Move the slider control to the left until you reach a size you’re happy with. A value of around 1 GB should be sufficient for most people.

A few settings, however, can only be adjusted by manually editing the values stored in the registry – specifically, in this key:

HKLM\SOFTWARE\Microsoft\WindowsNT\
CurrentVersion\SystemRestore

If you are an experienced Windows user and you’re comfortable working with the registry, you can change the interval at which restore points are automatically created. All the standard warnings apply here: Editing the registry is dangerous. You can screw up your system and even render it unable to start. If you do, you’re on your own. Just so we’re clear…

Normally, System Restore automatically creates restore points every 24 hours. To adjust this interval, change the value RPGlobalInterval from its default setting of 86,400 seconds (24 hours). Cut this figure in half, to 43,200, if you want to save restore points twice a day; triple it, to 259,200, if you want restore points created every three days.

By default, System Restore deletes restore points after 90 days. To adjust this interval, change the value RPLifeInterval from its default setting of 7,776,000 seconds (90 days). A value of 2,592,000 seconds (30 days) should be sufficient.

If a Windows program is giving you problems, one common troubleshooting tactic is to uninstall it, using the Add or Remove Programs option in Control Panel. What should you do if the pesky program isn’t in the list of installed programs? Although it sounds paradoxical, sometimes the best solution is to reinstall the program. After completing the program setup, check the Add or Remove Programs option again; you may discover that now you can uninstall it.