The following call disables File-System-Redirection on 64bit Windows in WOW mode (e.g. Accessing Program Files and ending up in Program Files (x86)):

// Minimum client Windows XP Professional x64 Edition or higher
// Minimum server Windows Server 2003 with SP1 or higher
NativeMethods.Kernel32.Wow64DisableWow64FsRedirection(pt1);