I run a laptop operating Kubuntu LTS [Dapper - not upgraded yet] and
have installed my preferred browser and mailer - Firefox and
Thunderbird with no problems. In fact the whole system has operated
far far better than XP ever did. However there is one small irritating
problem, When using FF and I find a "mailto" link in a web page, I
can't click on it and send mail to either mailer, Kontact or
Thunderbird. This is surely a matter of a hopefully simple association
somewhere but I'm damn'd if I can find it. More of a puzzle than a
real problem.

Using Konqueror of course I have no problem whatsoever as it hands off
the mailto directly to Kontact.

I intend soon to remove XP altogether and either install another
distro for learning purposes, or indeed install HH LTS in its place
and once running nicely, remove the old edition LTS currently in use
and expand the first partition accordingly.