explorer.exe - Windows Environment Functionality
One of the core processes used by the Windows OS is explorer.exe. It provides the basic windowing functionality required for management of the desktop environment. Every time you open a new window, use the Task Bar, Start menu, or File Manager, explorer.exe is responsible.If you use End Task on explorer.exe, the user interface (desktop) will be terminated. All icons, the Task Bar, and Start menu will vanish, along with your desktop wallpaper. Other running processes (e.g. Office, mail clients, etc.) should not be affected. Generally, Windows will restart a terminated explorer.exe process on its own, but this cannot be guaranteed and it's generally inadvisable to attempt this unless you know what you're doing.
On occasion, the explorer.exe process may go into a state during which it consumes excessive CPU time. This causes a detrimental effect on system performance. Other applications become very sluggish and unresponsive. The easiest way to check this is to open the Task Manager and watch CPU usage. If explorer.exe is consuming large amounts of CPU, it's best to reboot your machine. If this happens, it's likely due to a defect in Windows itself and does not necessarily mean your machine has been attacked by a virus.
While this is a legitimate Windows process, the file name can still be hijacked by malware of various types. Some reports have been made of dialer processes running under the name of explorer.exe. These should be relatively easy to identify based on the location of the file on disk.
The legitimate explorer.exe file will generally be found in c:\windows. If you find a copy elsewhere on your disks, or discover multiple copies of processes called explorer.exe running simultaneously on your machine, it probably means malware is infesting your machine.
As always, if you suspect a malware infestation you should download and run a current copy of an antivirus/malware scanner in order to isolate and remove the offending application. Be sure to obtain the most recent definition files, since these are critical to the removal of current malware variants.
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