Windows XP boot.ini: what's the /NoExecute option?

I would appreciate it if someone would look at my boot.ini
" [boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS= "Microsoft Windows XP Home Edition" /fastdetect /NoExecute=OptOut "

I have seen other boot.ini files with the last part reading "OptIn ". What is the significance of that? Any data look incorrect?

P.S. A minor point. My original OS installation was OEM WinXP Home. I installed WinXP Pro (full retail CD) over that with no problems well over a year ago. The boot.ini was apparently never updated. It does not seem to affect perfprmance, unless this is important for some reason. The only place it seems to show up is when I boot into SafeMode (if I remember correctly). I just ignore that the PC-DOS screen asks if I want to use Windows XP Home (which I no longer have on the PC--at least not as a separate OS).
Thank you.

 

For an explanation of the Data Execution Prevention (DEP) switches (Optin, etc.), see
http://support.microsoft.com/kb/875352/en-us

 

Thanks for the responses.
Looks like OptIn is safer, correct? Any downside?

 

Hi Jim,

A thread from last year on this.

http://www.windowsbbs.com/showthread.php?t=44289&highlight=OptIn

Regards - Charles

 

Per the link provided by charlesvar, and Arie's post in it
http://www.windowsbbs.com/showpost.php?p=237568&postcount=12
it seems "NoExecute=OptOut" is the most secure setting.
Since I have been having no problems with OptOut, I will leave my boot.ini as is.

P.S.--My DEP tab in System reads as did martinr121's in the linked post. The bottom says "Your comuter's processor does not support hardware based DEP. However, Windows can use DEP software to help prevent some types of attacks. "