The usual thing people using Outlook Express on Windows XP do when they have to go beyond XP is to forget about the current mail program from Microsoft (Windows Live Mail) and switch to Thunderbird from http://www.mozilla.org/thunderbird
It can import your Outlook Express mail folders when you setup your new Windows 8.1 PC (after you copied the Outlook Express data to a USB-stick).
Two big advantages I found are:
- it comes with built in search, so there is no need to rely on Windows Search for your mail as you did in XP
- all settings (including the address book) are in one Windows folder (you can have another folder for the mail) so it's easy to backup or copy another PC
I still have XP sp3 and using Outlook Express. If I get a Windows 8.1 computer what do I do about email? Currently I immediately download and save my emails to my computer and delete them from the Comcast server.