Microsoft and DEP

I just did a fresh reinstall of XP pro (with updates and SP2).
When installing some programs I got this pop-up saying DEP was blocking the program from being installed - assuming because according to Microsoft it's bad?
Isn't that supposed to be a Vista thing? This is the first time I've encountered this DEP in 4-5 years of using XP...what's going on???

 

The program has a fault to it, which caused DEP to freak out. Its been around since XP SP2, IIRC.

 

So a fault to it means what...?
Something in the programming of the program itself that XP doesn't like?

As I said before, I've never encountered this before and I must have installed XP at least 3-4 times and updated it without this before (with those very progams).

 

Something in the program set off DEP. DEP is provided to prevent buffer overruns in memory, which can lead to the OS crashing.

Im a little rusty on DEP, but thats it in a nutshell.