I'm not an AOL user, but I'm pretty sure they use standard POP3 and SMTP servers just like everyone else so you should be able to configure some other email client to use them if you have the proper info for the settings.
That being said, do yourself and the rest of the Internet a favor and don't use Outlook Express. The last thing we need is one more person to potentially be spreading the latest email worm because they were using Outlook Express, the favorite target of these people. Get a copy of Mozilla and use it's email client, or there's always the stand alone version of the same product called Thunderbird. They're free, fairly small, and the only feature they lack over Outlook Express is being able to access Hotmail accounts, but you do gain a spam filter that learns and becomes increasingly accurate at flagging spam the more you use it.
some asked me if AOL required customers to use the AOL email client,you could not use Outlook Express etc. True or urban legend ?.