Recently I was helping a client move their data from their old Windows XP machine to a new Windows 7 unit. They were concerned about changes in the mail program that Windows 7 provides compared to their old Outlook Express. They asked if Mozilla Thunderbird would be a good equivalent mail client, which I assured them it would be. Better in fact.
If you’ve ever tried to get your new installation of Thunderbird in your new computer to pickup all account settings, mail and address books from the old Outlook Express on the old hard drive, you know that can be problematic. An easy solution is to install Thunderbird first on the old computer, and have it import all account settings, mail, address books, etc. from Outlook Express.
Then, when i connect the old hard drive to the new computer to copy the users documents and other data, I simply replace the Thunderbird folder in the new computer located at C:\Users\UserName\AppData\Roaming with the Thunderbird folder from the old C: drive, which in XP is located in C:\Documents and Settings\UserName\Application Data.
Works like a charm!