kppp and harddrake don't have anything to do with each other.
UNIX (and hence Linux) was designed to be a networked operating system, and the prospect of having a network connection that you wouldn't want to use most of the time wasn't really a design consideration. As a consequence of this, the interface to establishing a modem connection is a little archairc, hence the need for programs like kppp and harddrake.
Kppp is a part of KDE that lets the user enter dial-up numbers and account information to establish internet accounts, much like under Windows. Harddrake (presumably) sets up the traditional dialing and CHAT scripts, that kppp ignores.
I don't know why it wouldn't work in Kppp; normally it works straight off but some fiddling with the configuration may be needed in some cases, especially if your ISP has obscure settings.
You could look at other internet dialers (SuSE uses kinternet, which works very well), if you can't get kppp to work and you don't like harddrake. Otherwise, look at the scripts in /etc/ppp/ and read http://www.tldp.org/HOWTO/PPP-HOWTO/
if you want to do it yourself.
— Robert J Lee.