1. Locate the Firefox profile on the Windows partition. On my installation, my Windows XP partition is first. Unless you do something weird and move your profiles, they are usually located in

   C:\Documents and Settings\[username]\Application Data\Mozilla\Firefox\Profiles\[profileid]

   , where username is your username (e.g. peter) and profileid is the randomly-generated profile identifier from Firefox (e.g. f39ojr4y.default). On my Ubuntu installation, this same directory is available at

    /media/sda1/Documents and Settings/peter/Application/Data/Mozilla/Firefox/Profiles/f39ojr4y.default

2. Locate the Thunderbird profile. Mine is at

   C:\Documents and Settings\peter\Application Data\Thunderbird\Profiles\wajy8lnr.default

   Again, substitute in your own username and profile id here. In Ubuntu, I see this directory as

   /media/sda1/Documents and Settings/peter/Application/Data/Thunderbird/Profiles/wajy8lnr.default/

3. Fire up Firefox and Thunderbird in Ubuntu, then close them down. You must have used Firefox and Thunderbird at least once in Ubuntu before doing this next step, or you won’t have locations for your default profiles.
4. Locate your Firefox and Thunderbird profiles in Ubuntu. These are in

   /home/peter/.mozilla and /home/peter/.mozilla-thunderbird

   (again, substituting peter for your username on Ubuntu). Under each of these directories you will see two other unique profile ids (e.g. vkuuxfit.default and 05zsr2ut.default). Note that there is no correlation between the profile names on Windows or Linux.

5. Back up your current profiles, just in case.

   cd ~/.mozilla/firefox ; mv vkuuxfit.default vkuuxfit.default.orig

   cd ~/.mozilla-thunderbird ; mv 05zsr2ut.default 05zsr2ut.default.orig

   Note that you must replace my profile names show above with the profile you see listed there. If you try copying and pasting exactly what I have above, it almost certainly will fail.

6. Symbolically link a new Firefox and Thunderbird profile to your existing Windows profiles:

   ln -s /media/sda1/Documents and Settings/peter/Application/Data/Mozilla/Firefox/Profiles/f39ojr4y.default ~/.mozilla/firefox/vkuuxfit.default 

   ln -s /media/sda1/Documents and Settings/peter/Application/Data/Thunderbird/Profiles/wajy8lnr.default ~/.mozilla-thunderbird/05zsr2ut.default

   Note that you must again substitute your Windows and Linux profile names where I use mine or it will not work. I colored the Windows profiles in blue and the Ubuntu profiles in brown so you can identify the target and the source more easily.

7. Now, fire up Firefox and Thunderbird, and you should see exactly the same configurations as you have on Windows.

Notes:

• This procedure overwrites your Linux Firefox and Thunderbird profiles with what's in your Windows profiles. It is possible to go the other way and preserve these, but I am assuming most of my readers are migrating from Windows to Ubuntu, not the other way around.
• You must shut down Firefox and Thunderbird before booting into the other OS and launching these apps. If you hibernate your system, leaving them running, you will receive errors when you boot into the other OS and try to launch the apps.
• Note that on Ubuntu your Firefox profile lives under ~/.mozilla/firefox and your Thunderbird profile is under ~/.mozilla-thunderbird.
• If you plan on mounting your existing Windows partition as a VMWare or other virtual machine image, don't do this. It will cause simultaneous writes to happen by the virtual machine and Firefox and Thunderbird. Not good.

The original post can be found here