According to the FTDI App note #104 (You are not allowed to view links.
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Login - see section 3), FTDI no longer provides a driver removal tool. However, they do provide a little information about how to manually do it (if you can't get the device to show up in the Device Manager).
Here's a practical procedure:
1. Open a Command prompt on your Windows XP system (Start > All Programs > Accessories > Command Prompt).
2. In the DOS box (command prompt), enter 'CD \windows\inf' (without the quotes, replacing "windows" with the location for your windows installation, if necessary, making sure to use backward slashes). Press Enter.
3. Type 'find "VID_0403&PID_6001" /I oem*.inf' (using double-quotes around "VID_0403&PID_6001"), and press Enter.
4. There will (probably) be a long listing of files. Scroll back through the list, looking for entries that show more than just the filename. Some will show contents like this:
%USB\VID_0403&PID_6001.DeviceDesc%=FtdiBus.NT,USB\VID_0403&PID_6001
%USB\VID_0403&PID_6001.DeviceDesc%=FtdiBus.NTamd64,USB\VID_0403&PID_6001
USB\VID_0403&PID_6001.DeviceDesc="USB Serial Converter"
Note the filenames for these files. In my case, they're OEM109.INF and OEM110.INF (yours will probably be different).
5. I'd suggest RENAMING these files with a new extension, so they can be easily restored if it creates any problems. Do this by entering 'rename OEM109.INF OEM109.OLD' (replacing "OEM109" with the correct file names for your system).
6. Now, you have to do some of the same stuff for the actual driver files. In the DOS box, change directories by entering 'cd c:\Windows\system32\drivers' and hitting Enter.
7. Rename the "ftser2k.sys" and "ftserui2.dll" files to something like "hideftser2k.sys" (I'm adding "hide" before the file names, so Windows won't see them, but you can easily find them if necessary).
8. Change directories to C:\Windows\LastGood\system32\drivers. Rename the "ftser2k.sys" and "ftserui2.dll" files as above.
9. Reboot the system.
You should now be able to connect the dongle & re-attempt the driver installation.
I'll try to provide more detail later...
--Dave