FileExists
FileExists(var FileName)
  This function simply checks if a file exists or not. It returns 1 if the file exists and 0 if it doesn't.
 
  Example:
 

function main()
{
     if (FileExists("C:\\Autoexec.bat"))
     {
          MessageBox("Autoexec.bat exists","Found File",0,0);
     }
}