Windows Mail cannot do much with identities except import them and then
mostly ignore them.

Windows Mail does allow you to connect to more than one email account
for the same Vista user, but puts all the incoming mail for these accounts
into the same Inbox.

If you need to keep mail from these accounts separate, you might consider
downloading and installing Windows Live Mail, which uses a separate set
of Local Folders for each email account:

http://get.live.com/wlmail/overview

Five possibilities:

1.  Use different Windows Users

2.  Make new folders and make a message rule like this:

Apply this rule after the message arrives
Where the message is from the mail.fjsmjs.com account
Move it to the fjsmjs folder
   and Stop processing more rules

3. Use Windows Live Mail which has separate folders for each account:
http://get.live.com/wlmail/overview

4. Buy WMIDs  http://www.oehelp.com/WMIDs/Default.aspx

5. Enable the Account column in the Inbox.

Now all of this is assuming that you are the only one using these accounts.
This is what I have done, as I have multible accounts on a server and it
works great for me.

Go to Tools -> Accounts -> Add
Once you have added the account(s), create folders for the accounts.

Create rules for so that the email for each account goes into the specific
directory for that account.
Go to Tools-> Message Rules-> Mail Rules-> New-> Select the Conditions for
your rule-> Where the message is from the specified account -> Select the
Actions for your rule-> Move it to the specified folder-> Rules
Description-> Name the rule-> click OK

The only thing that you need to do is to make sure that when you are sending
an email that you are sending it through the correct account.

(boilerplate reply)
You can add multiple accounts, but Windows Mail doesn't have identities or a
password option....
Windows Mail puts email from all accounts into the same Inbox, and there's
no setting to change that.  When you send a message, you can select which
account to send from, by clicking on the From: box.

Here are a few alternatives...

1.  Create folders for each email account and create message rules to move
email addressed to each account into the appropriate folder.

2.  Create and use different Windows Users, each with WM accessing only
their email account. (This is how you set a password to keep other users
out.)

3. Use the newer Windows Live Mail which has separate folders for each
account, but no identities or password:
http://get.live.com/wlmail/overview

4. Purchase WMIDs which adds identities to WM
http://www.oehelp.com/WMIDs/Default.aspx

5. Use Windows Mail for one account, Windows Live Mail for another.