Converting unmanaged VC++ code into managed code

Can someone explain how a  project written in unmanaged VC++ ts converted into managed VC++.NET code? I am following the instructions given in the following link:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcmex/html/vcconAddingMCToExistingApplication.asp

Unlike what the link instructs, however, clicking on the target project’s Property Pages->General->C/C++ does not offer an option Compile As Managed. The only way to get to an option Compile As Managed, so that Assembly Support (/clr) can be chosen, is when one clicks on the individual .cpp files.

It turned out, however, that even finding that was not enough to compile correctly the individual .cpp file. One needs also to change the Debug Information Format and the Code Generation->Basic Runtime Checks.

After all the above was done on the individual .cpp files, the files compiled correctly. However, it turned out that if one closes the project and opens it again the changed parameters in the said .cpp files are not retained. The project continues to be unmanaged despite the changes that one has made during the first opening the project.

What should be done to really convert an unmanaged code into a managed one?