Under restricted user account on Vista, you may get write successful when writing to the program files folder. These files get virtualized to a different folder, so that old applications continue to run on Vista.

When you actually go to “Program Files” in a Windows Explorer and see there will be no files there.

The file was redirected to the users’ folder. The virtualized directory is a hidden folder, to expose this view go to Organize: Folder options, from a Windows Explorer and then on the view menu, click “Show Hidden Files and Folders”.

Then go to c:\Users\{username}\AppData\Local\VirtualStore\Program Files\ and see that the files are created there. This is just a mitigation and not a feature of Vista.