|First of all, there is no Thunderbird version 20.1.|
The latest stable version is Thunderbird 17.0.5.
Newer Thunderbird versions are beta releases.
Download and install and start Thunderbird v17.0.5 at the new computer by clicking here
Cancel any configuration and close Thunderbird.
1. [OLD] Click "Start / All Programs" and rightclick Mozilla Thunderbird.
2. [OLD] choose "Properties"
3. [OLD] append " -p" without quotes to the target line and click OK button (NOTE: there is a whitespace infront of the -p)
4. [OLD] leftclick "Start / All Programs / Mozilla Thunderbird"
5. [OLD] now, the Thunderbird Profile Manager gets started and you'll see one profile listed, named default. Put the mouse cursor over the profile name and you'll see a yellow info box, showing the path to the location of the profile folder. Write this path down, we need it later on. Close Profile Manager by clicking exit.
6. [OLD] open Windows Explorer and navigate to the profile folder, e.g. C:\Documents and Settings\<YourUserName>\Application Data\Thunderbird\Profiles\something.default
7. [NEW] figure out the current Thunderbird Profile location the same way as described in steps 1 to 6 and copy the whole folder "something.default" to a USB-Stick.
8. [OLD] delete the " -p" in "Startmenu / All Programs / Mozilla Thunderbird" so, that Thunderbird can be started in it's normal way.
9. [MEW] plug in the USB-Stick to your computer and copy the whole content of the copied folder into the new profile folder at the NEW computer. Overwrite all files when asked. DO NOT COPY THE FOLDER SOMETHING.DEFAULT ITSELF, ONLY THE CONTENT!!!
10. [NEW] do step 8 on the new computer
Now you should be able to start Thunderbird from the Startmenu and all emails, accounts and settings should work fine.