The USBSER.SYS file does not go in the Arduino folder and I think that is where you are going wrong.
There was one more method (again time consuming)...
Not mine but it is an old fix that did work once upon a time.
It assumes you know how to create a .BAT file (batch file)
The last method is aimed at win 7 but should be fine also on VISTA.
Link for that one is here but it is a little more time consuming and you do need to take care following the instructions to the letter!