Migwiz really is a Wizard. It just works
Have a I mentioned how much I like the migwiz? Easier to type than "Windows Easy Transfer"
Just make sure the Old Computer has email in OE, Outlook or similar first. (Export it to that if need be). Getting it in in any other format is doable, but tricky.
But if you don't use OE
Here's how to get out of Thunderbird and into WLM (Windows Live Mail - and presumably Window Mail for those poor Vista straglers).
On the OPC (Old Computer), install and run the quaint little program. (gotta look it up again..) Watch out - it appears to fail on first run, but succeeds after a few tries. Found the HowTo here. The process is an export to .eml files using Tbird2OE and then import into Mail using OEImportEml. Both need to be installed. The import failed for me as I think there were some dodgy and/or large email files, so I manually dragged the files by folder (as described below) ..
Then copy all the resulting folders and files across to the NPC. (New PC)
Create the same folder structure in WLM. Select all the .eml files and drag and drop into the respective folders, (or just lump everything into the Inbox and forget about folders - who needs 'em?!
It might pay to use a dos batch file to move all the .eml files into one folder (eliminating the folder structure altogether) if you are not going to use folders in Mail.
Hang on, you can't do that as the .eml files are named 0000001.eml, 00000002.eml .. in each folder. You could rename them in the batch file I suppose - didn't try that.
(Don't worry, they translate OK back to meaningful subjects, to and from etc as they were originally).
I have to say that this is one case where drag n' drop really does work. (In fact I'm not sure there is another way to get the files into Mail)! Import is available on the file menu, but specifying the source each time would be a pain.
A interesting "by the way"
From a second hand PC, I have seen it pull in the complete email profile from the former owner! The current owner had no idea that info was on there - and I bet the former owner would not have been pleased either...
Another FYI, use the Win7 version of migwiz (copy it onto a usb stick and run from there on the OPC) Don't use XP's version.
Hallelujah - all praise be to win7 (and free apps that really work)