DEP is a built in mechanism that closes running programs that it thinks are threats to Windows so on your system, sometimes explorer.exe appears threatening and it should not.
The explorer.exe is a pretty important piece of Windows machinery and being so fundamental, it is also a prime target for malicious software.
You can tell Windows to allow threatening programs to run by adding them to a DEP exception list, but explorer.exe should not be added as an exception. It may then run, but that is not a solution to your issue. It sounds like explorer.exe is either afflicted with malicious software or needs replacing.
Let's run some free scans for that and then fix what is left over:
Download, install, update and do a full scan with these free malware detection programs:
Malwarebytes (MBAM): http://malwarebytes.org/
SUPERAntiSpyware: (SAS): http://www.superantispyware.com/
They can be uninstalled later if desired.
Edited by joseibarra, 01 November 2009 - 09:39 PM.