This post is coming to you from my brand new W-7 box, brought to you by Microsquash's reluctance to support a perfectly good OS (XP) any longer.
The good news is that the Mozilla apps can be transferred seamlessly using mozbackup. All my bookmarks, e-mails, folders and the like on Firefox and T-bird moved over with no problems.
The bad news is that XP has a program called Windows easy file transfer wizard that will move the contents of your old computer to your new one via a cable or network connection ot onto a solid state disk. W-7 has a similar program with a different name that works the same way, but labels files transferred to the HDD differently so it can't see the files transferred by the XP machine. So it's cables or nothing. What fun.
The description of the cables is nebulous enough to me that I'm not sure if a simple USB-USB would work or if I need something fancier with a nuclear booster box built into the middle. Guess I'll find out tomorrow.