By default, DEP is only turned on for essential Windows operating system
programs and services. To help protect more programs with DEP, select Turn on
DEP for all programs and services except those I select.
Per-program DEP configuration
For the purposes of program compatibility, you can selectively disable DEP
for individual 32-bit programs when DEP is set to the OptOut policy level. To
do this, use the Data Execution Prevention tab in System Properties to
selectively disable DEP for a program.
A detailed description of the Data Execution Prevention (DEP) feature in
Windows XP Service Pack 2, Windows XP Tablet PC Edition 2005, and Windows
Server 2003
http://support.microsoft.com/kb/875352