My guess is your hitting a firewall issue.

Your email client probably requires an open tcp connection on port 25, your ftp site requires an open tcp connection on port 21.

First I'd check your firewall and make certain both of these ports are open in your "exceptions" - if they are, then odds are good your router is for whatever reason routing these ports somewhere else-  Check your router and make sure you either have rules routing these ports to your pc or your pc is setup in the "DMZ" so that everything gets routed to it.

Both the FTP client and the mail client will require a clear path both in and out on those two ports.  Anything that interrupts that path will cause the problems you've described.

If you reinstalled Windows XP odds are good that the Windows firewall has both of those ports closed down - so you'll almost certainly need to go and add both port 21 and port 25 to your exceptions list.  You can find more detail instructions on how to add a port to your exceptions list for the windows xp firewall here:

http://www.windowsecurity.com/articles/Customizing-Windows-Firewall.html

The example they give is for opening a port for a web server (port 80), however in your case you'll want to substitute 21 for your FTP client and another entry on 25 for your mail client.. you can name them anything you want, the name isn't important, only that the port is added to the exception list.  Both of these ports should be specified as TCP.

Once those ports are opened if it's still not working then check your router settings, assuming you have a router on your system, and make sure the ports are forwarded to that particular machine or that that machine is in the DMZ so that all ports get forwarded to it.

You can find instructions on how to do this based on which router you have, since it does vary somewhat from router to router, but a quick google search should do the trick if it turns out you need to play with your router settings.

Hope that helps!
Stepdad