Data execution Prevention is feature that is defaultly enable in windowsxp sp2.
The purpose if Data Execution Prevention(D.E.P) is prevent malicious code running on a system.
You can make it available to cetain programs and services except that you can choose .
You can read he discription of DEP at http://support.microsoft.com/kb/875352
You can do that by start->settings->controlpanel->system->advanced->performance->settings->select ->turn on Data Execution prevention for all programs and services except those i select->clik->add and add the program you to exception from DEP.
How to Turn off DEP
you have to make adjustments to Bootfile to turn it off
You can do that by start->settings->controlpanel->system->advanced->Startup and recovery
->settings->edit
Replace the text that says /NoExecute=OptIn
so that it says /NoExecute=AlwaysOff
You can read the full explanation at http://www.housing.hawaii.edu/resources/support/turnoff-dep.htm