I get a DEP or Data Execution Prevention error message

Go to Start > Control Panel > System > Advanced > Performance > Data Execution Prevention.

Select "Turn on DEP for all programs and services except those I select:"
Select "Add", navigate to C:\Program Files\Steam (or your default Steam directory), and add Steam.exe to the exception list.

Additionally, you will need to add the executable (fm.exe, in this case) for any game you are seeing issues with. These files will either be in Steam\steamapps\common\<Game Title> or in \Steam\steamapps\<Your Steam Account Name>\<Game Title>

I have a problem with this solution: if I try to add fm.exe to the list, I get a message telling me I cannot prevent this program from being launched with DEP. (The steam executable is no problem.)