Because of the way EXE files are loaded into memory and run, their instructions cannot be protected against a low level program that is able to read kernel memory directly. One such program is called ProcDump32. Thinstall has a security feature that will make it difficult to reconstruct your original EXE if procdump is used. This feature can be found under Link -> Program Security.
Destroy PE Header - This option causes Thinstall to partially protect your program against reconstruction of an unprotected EXE using memory dumps. It works by not loading the parts of your executable into memory that are required to perform a successful image dump, while leaving the parts of the EXE necessary to run intact. In some rare cases this could cause your program to fail to load.
Disable .NET Profiling - .NET provides a mecanism where a "profiler" can be registered on your system. Profilers are loaded as external DLLs and recieve callbacks from the .NET Framework when various events occur, including when assemblies are loaded. For developers interested in protecting their applications against reverse engineering, this option is safe to use.
Enable Anti-ProcDump - When enabled, any attempts to apply "ProcDump" to your program will result in the message "Program cannot be dumped!"