Windows 2000 pro: Dynalink ISDN Card won't install

This has to be dealt with with a certain urgency (It's one of my customers) - This guy had win98se on his system and never had any problems with his Dynalink ISDN Card (I believe it's 128 PPH+). I've seen it myself, as I re-installed this card on the win98se OS without problems. However, after installing the update to Windows 2000 professional (I really have no idea why he needs it - but he does this sort of thing all the time on 2 pc's one of them began showing problems with the card, probably because he switched ISP's and screwed up some settings. So I said to him, "Just give me the original CDs and I'll re-install the card." Cause that's the most obvious, the easiest and the fastest solution, right?? So now I'm stuck with win2000pro not wanting to install from the original drivers... It just doesn't see them at all when I let it scan for the best drivers on the CD. I downloaded all versions from the dynalink website but none of them work. What do I do now?? I don't want to format his hard disk, that seems so absurd - it's just an ISDN card!! Please help me out guys - ToXiK