PROBLEM UPGRADING FROM FC2 TO FC6

[Steve Dawes]

You cannot upgrade from 2 straight to 6.
There has been too many significant changes to make such a version jump.
Your best bet is to tell the installer that you are installing, (not
upgrading).
If you are worried about loosing existing data, then I strongly recommend
that you backup all your data before you proceed with the new install.

In fact, regardless, you should always do a backup of your data, and
configuration directories as part of an upgrade or fresh install process.

Good luck.

Steve