You can select certain programs you install from being effected by the DEP process but it won't work for IE 7! With the boot.ini file method outlined on the MS page you can always reverse the process with another edit of the boot,ini file.
The second of the two seen in the advanced you named there was tried out in Vista to get nowhere already. I still had to switch off the DEP itself to see IE 7 working again.
This is I suggested the other method in case that doesn't work for you there with XP. When that was tried here the iexplorer.exe file itself vanished without a trace!
The other option besides the edit of the boot.ini file would be using the system restore feature if you still have any restore points prior to when the problem was first seen. That will restore the system registry to see if that will work better.