I receive e-mails into my Outlook Inbox (george@abc.com) from a
variety of POP e-mail addresses (george@abc.com, georgew@def.com, et
al)  I want to respond to each message with a "From" line and
signature consistent with the e-mail address to which the message was
sent.  Of course, now I only have "george@abc.com".

How do I set this up?

George: 

Hi. I'm going to answer this as if you're using Outlook 2000, although
I have used other versions of Outlook and I do believe the process
would be the same whatever the version.

When you say you receive e-mails into your Outlook inbox from a
variety of POP e-mail addresses, I'm thinking you must have different
Mail Accounts set up under the "Tools" menu.

If you go to "Accounts" under the "Tools" menu and select the "Mail"
tab, it should tell you how many accounts, or profiles, you have set
up. Basically, the process will be for you to set up a separate Mail
Account for each address you want to have as a "From" address.

If you already have Accounts set up for your different POP addresses,
here's what you do:
1. Highlight the Account name
2. Push the "Properties" button
3. On the "General" tab, for user information, put the name you'd like
as a "From" name, and for e-mail address put the "From" address you
want to use.
4. The other key set-up info is on the "Servers" tab. The incoming
mail blank should be filled in with the name of the POP server where
the mail is coming from. The outgoing mail (SMTP) needs to be the mail
server for the Internet Service Provider (ISP) you're using to connect
to the Internet when you send the mail. That might be something like
mail.earthlink.net, if you're using Earthlink. You might need to
contact your ISP or the IT guy at work to find out the proper SMTP
server name. The easiest way, though, is probably to look at the
profile for the address (george@abc.com) that you're using to send
mail right now. You can use the same outgoing server name for every
Account.

If you don't already have accounts set up for each e-mail address,
this is the process:
1. Start from "Tools," drop down to "Accounts" and select the "Mail"
tab
2. Press the "Add" button 
3. Select "Mail". A wizard should pop up. 
4. Under "Display Name" put the name you want the e-mail to be from
5. For e-mail address, put the e-mail address you want the e-mail to
be from
6. For incoming mail, you can leave it blank unless you need to
retrieve mail (and it sounds like you've got that covered). For
outgoing mail, you enter in the name the mail server for the Internet
Service Provider (ISP) you're using to connect to the Internet when
you send the mail. That might be something like mail.earthlink.net, if
you're using Earthlink. You might need to contact your ISP or the IT
guy at work to find out the proper SMTP server name. The easiest way,
though, is probably to look at the profile for the address
(george@abc.com) that you're using to send mail right now. You can use
the same outgoing server name for every profile.

Here's a Microsoft support document on setting up e-mail accounts:
http://support.microsoft.com/default.aspx?scid=kb;en-us;q195578

One caveat... If you are NOT using an Account to retrieve mail, you
should disable automatic e-mail checking on the account. You can do
that in the "Properties", "General" section when you're looking at
"Tools" "Accounts".

Once you've got the profiles set up, then it's time to use them. If
you're retrieving mail through the Accounts, the correct "From"
address and name should automatically appear when you REPLY to
messages.

If you are initiating messages, or want to check to make sure they are
going out from the right name, do this:
1. Compose your message.
2. Before you send, click the "Options" button on the outgoing e-mail.
Look for the "send message using" option. Use the drop-down menu to
select the proper Account you want the message to come from.
3. Close that dialog box.
4. Push send. 

Those steps should work for you unless your ISP has measures in place
to prevent you from doing it. In that case you'd just have to check
with your ISP or it might be impossible.

Now... getting that signature right. This is another manual process of
setting things up, which is very similar to the above.

1. From the main menu select "Tools" and drop down to the "Options"
menu.
2. On the dialog box that pops up, select the "Mail Format" tab. 
3. Use the signature picker to create or modify signatures for each
one of your "Accounts" set up above.
4.  Once you're done, select "None" where it asks you "Use this
signature by default" -- that way, you'll start each message with no
signature, and you can add it manually depending on the "From" name
and address.
5. When composing a new message, place your cursor wherever you'd like
the signature to go. Then go to the "Insert" menu, and drop down to
the "Signature" option. From there you should be able to pick the
appropriate signature from the different options,and it will appear
wherever you had your cursor.

I hope all of this is helpful and that it enables you to meet your
goals.

best,
Pamela

Terrific answer; this worked perfectly!  (Alhtough XP is a little
different from the instructions given, it was easy to figure out.)
Thanks for the guidance here!