Leave Windows XP to handle something like shutting down, and it will likely take its own sweet time about it.  Here are some things I did to light a fire under XP at quitting time:
    - Start Menu / Run... / Regedit / press ENTER
    - Go to HKEY LOCAL MACHINE\SYSTEM\CurrentControlSet\Control
    - Double-click the entry called WaitToKillServiceTimeout (or create it as a REG_SZ string value if it's not there)
    - Set its value to something lower than the default of 20,000 (I chose 1000)
    - Go to HKEY CURRENT USER\Control Panel\Desktop
    - Find the entry called AutoEndTasks (or create it as a REG_SZ string value if it's not there)
    - Set the value to 1
    - In the same list of entries, look for WaitToKillAppTimeout
    - I gave mine a value of 2000
    - Also in the same list, there should be one called HungAppTimeout, which I gave a value of 2500.

I read somewhere that the value for WaitToKillAppTimeout should be less than that for HungAppTimeout.  I gave whoever the benefit of a doubt, like I often do when I want to tweak something and am feeling lucky.

Here's a setting where I had to choose between safety and speed.  Some people (certainly those in the know about Windows security) would disagree with this one, but I had no choice.  It involves the ClearPageFileAtShutdown entry located at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management.  I discovered that when I set this to 1, the system took forever to restart or shut down.  Forever = around two minutes-- too long for me.  Until or unless I find a solution, the value will stay at 0.

I don't remember where I found the following three shutdown / restart / logoff commands... seems like just about every XP site has them.  They can make shorter work of doing these tasks. The -t is for timeout or delay:
    shutdown -s -t 00 (shutdown)
    shutdown -r -t 00 (restart)
    shutdown -l -t 00 (logoff)

Use them from Start Menu / Run..., the command line (Start Menu / Run... / type CMD / press ENTER) or as shortcuts on the Desktop if you like.

Type shutdown /? for more options.

Another way to log off requires that there be a Log Off option on the Start Menu.  If it's not there, TweakUI (one of the Microsoft PowerToys for Windows XP) has an Allow Logoff on Start menu entry in its Explorer category, which may be the easiest way to make Log Off available.  Also, if Log Off is the only item in the main branch of the Start Menu that begins with an L, you can minimize the number of key presses to reach it-- tap the Windows-logo key, followed by the letter L.  From there, you can choose the Log Off option, wait a bit, enter a password if prompted, wait a bit more, and you're back at the Desktop.  It's a lot faster than a reboot.

I was reminded of a free command line based tool by Steve Gibson, named Wizmo, which is discussed at a Langa url called Easy Automated Shutdowns.  This thing has some options that will amaze and astound, not the least of which are its shutdown / standby / hibernate / logoff / reboot functions.  You can also use it to open and close CD trays, mute or adjust audio volume, launch the Graviton animated screen saver, and lots more.  Read all about it and give it a go.

If you prefer, there is another free XP shutdown tool called Kill Win, found here.

More... more.... always more about Windows XP shutdown:
    - WINDOWS XP SHUTDOWN & RESTART TROUBLESHOOTING (Windows Support Center)
    - Resources to help troubleshoot shutdown problems in Windows XP (Microsoft)
    - Troubleshooting Windows XP Shutdown Issues (The Elder Geek)
    - How To Increase Shutdown Time So That Processes Can Quit Properly in Windows XP (Microsoft)