Data Execution Prevention (DEP) helps prevent damage from viruses and other security threats that attack by running (executing) malicious code from memory locations that only Windows and other programs should use. This type of threat causes damage by taking over one or more memory locations in use by a program. Then it spreads and harms other programs, files and even your e-mail contacts. DEP monitors your programs to determine if they use system memory safely. To do this, DEP software works alone or with compatible microprocessors to mark some memory locations as "non-executable". If a program tries to run code, malicious or not, from a protected location, DEP closes the program and notifies you.
DEP can take advantage of software and hardware support. To use DEP, your computer must be running Microsoft Windows XP Service Pack 2 (SP2) or later, or Windows Server 2003 Service Pack 1 or later.