I've convinced my parents (mostly my father) that it would be easier for them to have Kubuntu on their new laptop than Vista. They'll have to learn a new user interface anyway, but Kubuntu makes support for me much easiear (especially since I've learnt about the desktop sharing feature of NX).
So I've ordered a trusty Dell Inspiron 6400n like my wife has, but this time with Ubuntu 7.04 preinstalled. Installation of Kubuntu 7.10 went smoothly, thanks to Dell's Ubuntu support even the internal modem is supported by a restricted driver.
But when using KPPP for making an internet connection, I was not able to brwose the internet using konqueror. Firefox did work, so I set it up as default internet browser.
But some days later my father found out that he couldn't receive any mails in KMail, though checking with the web frontend I saw he had new mails. There was no error message in KMail, it just said there were no new mails.
Some googling later I found a bug report and knew that KDE software like Konqueror and KMail rely on KNetworkManager to check wether they are in online or offline mode. When it works, it's a great feature. Unfortunately it doesn't work with some weird WLAN setups -- and with KPPP!
The easiest solution to get around this is to simpy quit KNetworkManager -- and make sure it doesn't automatically come up again on the next start.