Vista and ProgramData

Data for all users should be stored in %ALLUSERSPROFILE%, or call SHGetFolderPath() with the parameter CSIDL_COMMON_APPDATA to get the all users storage area.

See http://www.deez.info/sengelha/2006/02/28/windows-vista-changes/ for more details.

This is because of folder redirection in Windows Vista. If you do not normally have the rights to write something into the C:\Program Files-folder, Vista will silently redirect those writes into a "secret" folder inside your user directory. The file will still be visible for the user who created the file (and any programs running as that user), but it will not be visible for anyone else. So your program is probably running as a different user than Explorer is, and thus Explorer cannot see it.

See the following output from dir /aL on my Vista 64-bit machine:

C:\ProgramData>dir /aL
 Volume in drive C has no label.
 Volume Serial Number is 74DB-58F8

 Directory of C:\ProgramData

02.11.2006  16:41    <JUNCTION>     Application Data [C:\ProgramData]
02.11.2006  16:41    <JUNCTION>     Desktop [C:\Users\Public\Desktop]
02.11.2006  16:41    <JUNCTION>     Documents [C:\Users\Public\Documents]
02.11.2006  16:41    <JUNCTION>     Favorites [C:\Users\Public\Favorites]
02.11.2006  16:41    <JUNCTION>     Start Menu [C:\ProgramData\Microsoft\Windows\Start Menu]
02.11.2006  16:41    <JUNCTION>     Templates [C:\ProgramData\Microsoft\Windows\Templates]
               0 File(s)              0 bytes
               6 Dir(s)  62 040 051 712 bytes free

The feature is known as reparse points or junctions, depending on where you read about them. They are very similar to symbolic links in Unix.