I have this modem (SmartLink/Lectron I56KSP-F00). I could not get the CD driver to work in Windows 2000. Nor any other driver I found, even here. This driver is made for the Asound Smartlink SL1900, which uses the same chipset as the KSP. It works in Windows 2000, and should in XP too, cause thats what it was advertised to work under.
I tested this with netzero for a little while on my client machine, so if there's any long-term issues (e.g. intermittent disconnects), please say so.