Maybe the following hint is a solution for Your problem. For me it works under Win2000 with active AVM boards (B1, C2, B1-PCMCIA). It is said to also work for Win-XP.
* Get the WinNT 4.0 driver for Your board from www.avm.de. The drivers for WinNT still include CAPI 1.1 support (at least for active boards).
* Open the executable installation program with e.g. WinZip (do not run it).
* Extract the file "capi32.dl_" and unpack it with "expand" to "capi32.dll".
* Copy the resulting file to "%SystemRoot%\system" - ready.