Would this page help?
Running XP Pro. Have SS and PMDX-126 BOB. When going through the 'New Hardware' routine while installing driver up pops the message - "The file 'ftdibus.sys' on FTDI Disk is needed." I'm unable to find file. How do I solve? Help!!!!!!!!!!
Problem solved. Basically had to uninstall/delete everything and start over. Greg at Warp9 was of great help. Here's what he sent me and it worked. Maybe it will be of help to someone else if they need to update driver.
You should be able to find a browse button and point it to the directory
where the driver files are located (where you unzipped them to).
If that does not work, I would try going into the Device Manager and
locate the SmoothStepper (it should be plugged in). You might find it
under "Unknown Devices" or the USB devices. Wherever you find it,
right-click on it and choose to either reinstall or remove the remove
it. That will give you the opportunity to start over (if you remove it,
then you will need to unplug it and plug it back in again).
If that doesn't work, then you should run the following program from
FTDI (be sure to unplug the SmoothStepper first):
There is a command-line version and a graphical version. I would run
the graphical. Here is a link to the readme for the graphical version:
You will need to enter "0403" for the Vendor ID, and "A650" for the
Product ID (don't include the quotes, and be sure that the "A" in "A650"
Then click "Remove Devices" and it will remove every instance of a
SmoothStepper from your system. Plug in the SmoothStepper and you
should be able to install it properly.