(I can open the files using notepad and can see the emails, but it's a pain trying to view them that way, anyone have any advice on how to view these in the manner in which an email client would?)

Not sure what support pages you looked at. There is no such thing as exporting a profile, and there is no need for it either. Follow these instructions: http://kb.mozillazine.org/Moving_your_profile_folder_-_Thunderbird#Create_a_new_profile_and_copy_the_old_one_over_it

But profiles are perfect for this. You don't need to import. Just copy the old profile from your old HDD over Thunderbird's new profile.

https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

If you already have things in the new profile you want to keep, then it's a bit more complicated. I'd install the biggest profile then import the mailboxes from the smaller one, using https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

Another tack is to copy the old profile in as a second profile, and use Thunderbird's profile manager to choose between them. But this makes your profiles mutually exclusive and combining material from one into the other is very hard.

https://developer.mozilla.org/en/Profile_Manager

Thanks for the responses guys, it's 2 am here so I'll give it a bash first thing tomorrow!

This was what I had followed: https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

Manual transfer required backing up the files (though is simply taking the folder enough?)

I tried the import-export-tools add on, but I couldn't figure out how to import the user profile / folder.

I had tried using the profile manager but for some reason it refused to even show the old folder.

Not too worried about any other email accounts, I can just make a temporary windows user and load it in there :)

Thanks again!

What I think you need to know is that windows hides the folder.

Start by telling windows to show hidden files and folders. See http://windows.microsoft.com/en-au/windows/show-hidden-files#show-hidden-files=windows-7. You old drive will not have an appdata (if our using Windows 7) folder that was not visible to explorer or search. Locating the Thunderbird folder in that is not difficult I am sure.

Now if you do not have an existing Thunderbird installation with mail in it. do the following.

NOTE your copying from and to folders with the same names. It is easy to become confused and do it backwards (Boy is is easy). Perhaps a interim copy should be made as a backup before you start.

This will delete any existing Thunderbird data mail settings etc so do not do it if you already have mail in a newly installed Thunderbird post back for alternate instructions.

Make sure Thunderbird is not running. In the start menu type %appdata% to load a windows explorer in the current drives appdata folder. Delete any Thunderbird folder in appdata on your new drive Drag the old Thunderbird folder to the appdata on your new drive Start Thunderbird Everything should be go.

When first reading that, I was worried something might be wrong with my backup, because that's exactly what I had done (prior to posting here).

Then I had another nose around, in the AppData folder there were two Thunderbird folders, one in AppData/Local and one in AppData/Roaming.

Originally hadn't noticed the Thunderbird folder in Roaming (I had only replaced the one in Local).

I'm such a Win7 newbie!

Thank you so much everyone, your time is massively appreciated!

All the best,

-Will

Then can you mark the thread as 'Solved' please? Thank you.