When I was moving from XP to the Windows 7 RC, I loaded Windows Live Mail on the XP machine. It found Outlook Express and moved everything - mail and accounts - over.
I then ran a program to save the Windows Live Mail stuff, installed Windows Live Mail on Windows 7, then restored Windows Live Mail from the backup. It restored everything. As I recall, all I had to do was put the passwords back in.
The program I used to do the backup is KLS Mail Backup - Freeware Outlook Express, Windows Live Mail, Thunderbird, Firefox backup