Sample that demonstrates the difference when running Visual Studio debugger in 32 bit instead of 64 bit as expected.

CheckForMarkdownMonster.cs

string mmFolder = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles),"Markdown Monster");                    
string path = sk.GetValue("Path").ToString();
if (!path.Contains(mmFolder))
{                        
    var pathList = path.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries).ToList();
    pathList.Add(mmFolder);                            
    path = string.Join(";", pathList.Distinct().ToArray());

    sk.SetValue("Path", path);
}