Window Messenger is not running on my system.

Hello to all,

I have a small problem my window messenger wasn't run on my system? My
operating system is Vista Home Basic. I tried to turn off DEP (date execution
prevention) but there was no turn off instead they were two options

1. Turn on DEP for essential windows program and services only
2. Turn on DEP for all program and services except those I select

I select no. 2 another problem is how could I know what kind of .exe are for
Window Messenger in able to not stop by DEP.

Thanks,