note: this probably applies to migration from windows 2000 or prior versions as well, but this note is based on the migration i did from windows xp to windows 7.

first you need to backup your old files. the files should be at default file locations specify below. alternatively, you should double check your settings. if you don't know how to, read this instruction.

default file locations

on windows xp (and windows 2000):

C:\Documents and Settings\<User Name>\Application Data\Thunderbird\

on windows 7:

C:\Users\<User name>\AppData\Roaming\Thunderbird\

setup on new windows 7 computer

do not run thunderbird after installation. do the following first.

(however, if you have already startup thunderbird prior to this step, read next section.)

copy the backup file to the default file location.

edit <path to thunderbird>\Profile\<random string>\pref.js.  replace all strings:

C:\\Documents and Settings\\<your name>\\Application Data\\....

to

C:\\Users\<your name>\\AppData\\Roaming\\Thunderbird\\.....

now run thunderbird. you may be asked to migrate data if you're running a different versio of thunderbird.

if you started up thunderbird prior to restoring backup files...

thunderbird creates a random-string subfolder in your thunderbird profile to store all related files. this is automatically done when you startup fresh.

this is something i don't like as it requires extra steps to setup to use your old files. it has been the way since thunderbird history and luckily there are solutions.

after you have copied the old files, note the name of subfolder with random string from your old profile.

edit <path to thunderbird>\Thunderbird\profile.ini (this should be in Profile's parent folder), look for 'Path='. replace the random string with the random string noted above. thunderbird will now use the old profile instead of the new one.