为什么不打开/写入/关闭路径为“C：/ filename”的文件在W7中返回失败？

I have a win32 program that I've supported for years. I just noticed that on W7 if it attempts to open/write/close a file directly in C:/, the system calls do not complain but the file is not created. I'm sure this has something to do with W7 security, but shouldn't the system calls return -1 to let the program know its not gonna work? It gets worse... After I realized that the system calls were not failing I figured I'd test for the presence of the file after the close() but that even succeeded! The file does not show up in explorer, but stat(c:/filename) says its there. This path is set by the program user, so how can I detect that the file operation is not successful if every system call I try tells me it was successful?I have a win32 program that I've supported for