Restoring KMail files and directories.

I have problems with my hardware, and am probably going to accept some loss of data. But I am particularly anxious not to loose all my KMail information. In the dim and distant past, I used to be able to copy across a .mail folder and bingo! I had my emails. Is there anything similar in KDE 3.5.10? My guesses were all wrong! FWIW, and in case it affects anyone else, I tried to use my Lenny /home, which is on a separate HDD, with TDE 3.5.12 or 3.5.11 (I have wiped it, and now can't remember which it was). KMail refused to function. So I reinstalled Lenny and 3.5.10, and KMail could not use the directories because the indices had been altered. KMail's offered attempts to reset the indices (and maybe lose a bit) failed to work. Obviously I ought not to have tried to go backwards, but there was not much other choice at the time!! So, alternatively, is there some way I could tidy up the "corrupted" copy? Thanks Lisi