When my PC is slow, I press Ctrl-Alt-Delete to close unnecessary programs. But there are programs running that I can't identify. What are they?

Eric Andersen, Arlington Heights, Illinois

All sorts of programs run in the background on your PC. Closing unessential ones is sometimes a good idea, because doing so can increase your system's speed and can help keep software installations trouble-free. Identifying which apps are essential and which are not takes some detective work, however.

Pressing Ctrl-Alt-Delete in Windows 98 and Me opens the Close Program dialog box, which lets you select an app and click End Task. In Windows 2000 and XP, this key combination brings up the more complicated Task Manager (in Windows 2000, you also have to click the Task Manager button after you press Ctrl-Alt-Delete). But fear not: You need to be concerned with only two of the Task Manager's tabs: Applications and Processes (see FIGURE 1).

It's easy to figure out what to close on the Applications tab because most of the names are easy to recognize, such as Quicken and Microsoft Word. Determining which processes you can safely stop is trickier. Click Processes to see a long list of open executable files. When you select one and click End Process, you're warned that this may crash your system. It probably won't, but save any open documents to disk before you try this just the same.

If you don't recognize a specific process listed in either Close Program or Task Manager, search your hard drive for the file name. That should give you a clue as to which program launched the process. Write the name down, and then click Cancel to exit Close Program. Select Start, Find, Files and Folders (in Windows 98), Start, Search, For Files and Folders (in Me and 2000), or Start, Search (in XP).

In Windows 98, enter the file's name in the Named field. In Windows Me and 2000, type the name in the 'Search for files or folders named' field. In Windows XP, enter the name in the field labeled 'All or part of a file name'. Select Local hard drives from the 'Look in' drop-down menu. Click Search Now, Find Now, or Search, and locate the file among those listed in the results pane to the right.

If that doesn't help identify the mystery process or application, enter the file name in the search field of Google or your favorite search engine. You're bound to find some useful information about the file.

Here are some of the programs that may mystify you when you bring up the Windows 98/Me Close Program window.

Explorer and systray: Keep these basic Windows components open at all times.

Rnaap: This program loads when you use dial-up networking, and it stays in memory until you close Windows. Close it; Windows will reload it if necessary.

Ctfmon.exe: Microsoft claims that closing this Office XP utility for voice recognition and other text-entry alternatives may make Office unstable. The program stops loading when you uninstall Office's Alternative User Input feature.

Some common processes listed in the Task Manager's Processes tab under Windows 2000 and XP follow.

Explorer.exe, LSASS.EXE, services.exe, system, and WINLOGON.EXE: These necessary parts of Windows must keep running.

Iexplore.exe: Ending this Internet Explorer executable file will cause all of your IE browser windows to close.

Taskmgr.exe: This is the executable file for the Task Manager program itself.

Svchost.exe: Often more than one copy of this host process for .dll files will be running. Though closing one of them probably would not cause any major harm, it could crash an application.

Msmsgs.exe: If you don't use Microsoft Messenger (not to be confused with Windows Messenger), you can close this program without problems.

Spoolsv.exe: This is your print spooler, so Windows probably won't let you close it, lest your printer starve for data.

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