What I do is this.
- Rename the existing Mozilla directory.
- Make a new Mozilla directory
- Install the latest Mozilla in the new directory, allowing it to convert my old Netscape account.
- Exit from mozilla.
- Copy as much of the old mozilla account over the new account as I want, but at least the entire account root. It'll be something like
F:\\warpzilla\\bin\\Mozilla\\Profiles\\<name>\\<weird_code.slt>. The fact that <wierd_code.slt> is different in the old mozilla doesn't seem to matter at all. I don't bother copying .\\Cache, .\\Mail or .\\News because I don't care about the cache and I don't use Mozilla for mail or news.
- Restart Mozilla, and I'm back where I was with the previous one.