Originally posted by: Gamingphreek
It is Data Execution Prevention. It is basically software (or hardware in the A64's case) that prevents the processor from executing potentially harmful code thereby preventing memory overflows. Sometimes however it prevents essential processes of a program from running in turn giving a blue screen.
It is a good idea just has some bugs to be worked out yet.
-Kevin
Actually, it's both. DEP is MS's term for both a software + hardware solution. The software part is (at least in part - there may be more) a set of re-compiled binaries for XP in SP2, equivalent in function to using Visual C's "/GS" (generate stack probes) compilier switch. The hardware solution is only currently provided by AMD64 CPUs, by their "NX" (no-execute) bit feature, which prevents execution of code from virtual-memory pages set as "NX", on a per-page (usually 4KB, but could be 4MB) basis.
An application-mode DEP exception will trigger something basically like a GPF, and tell you that the application has attempted an "illegal operation", executing code from a non-executable page, or a stack buffer overflow.
A kernel-mode DEP exception (which is what appears to be happening here), is basically like a BSOD, it triggers a system halt or restart. (If the video drivers themselves die, the system can't BSOD either, even in the case of a "normal", non-DEP-initiated system halt. The system will just freeze or reboot, in that case. I've been having that trouble myself recently, actually, although it has nothing to do with DEP or UT2K4.)