/noexecute=OptIn is a setting for computers with processors without hardware enforced DEP support which will enable software enforced DEP.
There are a couple of settings:
/NoExecute=OptIn (enables DEP for Windows system files)
/NoExecute=OptOut (enables systemwide DEP)
/NoExecute=AlwaysOn (enables systemwide DEP without pssibility of individual application exclusion)
/NoExecute=AlwaysOff (disables DEP completely)
I'm not sure what hardware you have, but it may be a problem described here: