Why would you need an extra email address?
Have you ever been on a site that insists you enter a valid email, then they mail you a password to that address. Then the spam arrives (that's why some sites want your email, but not all so don't get paranoid). But, no matter what, you are added to their mailing list. If you read the small print, some say that you may occassionally receive mail from 3rd parties. In other words, they may sell your email to some other company.
Get a freebie email account, generally referred to as a throw-away email from any of the major companies. Whoever you choose, don't use their install program as it may make it your default email and some install programs put their name in your browser window. Do print out all the information they give you as it's all needed, and configure it yourself.
Thinking up an email name
The more obscure the email address name is, the better, as it will be harder for automated systems to guess it. "xyz123abc456@your-isp-name.com" is fine. Don't bother trying to use your name, as will probably already taken anyway, and you're not going to use this one for family and friends. Common names will be hit by spam, example: "harry.white9283746@your-isp-name.com" will be found by automated spam within a few days. In fact, don't use any words that appear in a dictionary.
In Outlook Express, click Tools from top menu and select Accounts.
In popup window, click Add and select Mail.
Enter a suitable name for the account in Display name and click Next.
In Incoming mail (POP3) and Outgoing mail (SMTP) enter information given to you by the Service Provider then click Next.
Some common ones:-
If you haven't got them, visit the Internet Service Provider's help page.
In Account name enter your email (Some just require the account name).
In Password enter your password you choose or were given.
Tick Remember password, click Next and finally click Finish.
Now select the newly created account and click Properties.
In General - check settings you've entered are correct.
Untick Include this account when receiving mail as you don't want this account checked each time you receive mail.
In Servers - check settings you've entered are correct.
In Connection - leave the Always connect to this account using box unticked.
In Security & Advanced - don't alter these default settings.
Click OK then close Accounts.
If you make a mistake and things don't work out, go back into Accounts and click the one you've just created. Then either edit it, or click Remove and start again.
When retrieving your normal email, this new account won't be checked (unless you want it to be). Normally, you would only use this email address for sites that you don't trust, to keep your primary address safe.
To check mail from the newly created account, click the little arrow at the side of Send/Recv. A new box will appear. Scroll down the box and select the email account you want to receive from the list, then click it.
Note: Some email accounts can not be retrieved to your computer, so you may have to visit their website to compose, send and receive mail.
Google Mail
By far is best is Google's Gmail where you never need to delete another email again. Gmail gives you so much storage that you can keep all your emails (2 gigabytes at present). Enough to keep many years worth of messages. It can also be retrieved to your computer, or you can do it at their site. The mailbox is searchable to find messages that someone sent you maybe 9 months ago. Handy when you want to know exactly what someone said, and later denies it 
I've had a Gmail account for over a year now, and I think I've had just 2 spam messages that got through their filter. You can get one from mail.google.com if you like 
and did I mention that it doesn't cost anything at all!
