I have upgraded my PC and want to copy across my Kmail and directory structure into the new machines Kmail application. I have copied them directly into the new Mail directory but, although they are there, they are not shown in the Kmail programme. There is no option to import Kmail files in the import tool.

Any ideas?

Many thanks.

I have managed to copy kmail's mail form one system to another (But not my address book, or mail filters - I wish the kmail developers could fix this!)

First problem: Older versions of kmail kept mail in ~/Mail, newer versions keep mail in ~/.Mail. So make sure you are moving your mail to the correct directory!
Make sure your mail, once copied over, has the correct ownership (ie the new user on the new system).
I then deleted the *.index and *.index.ids files.
Then I started kmail. It was quite slow to start up, as it had to re-index several thousand emails, but then my mail was where it was supposed to be.

HTH