You can now create and manage multiple email aliases from a single Windows Live Hotmail account. The new aliasing feature makes it easy to create disposable email ID’s and use a different email address and still get all the benefits of Hotmail without having to change your primary email address and online identity.
Why would you want to create an alias?
Some people like to use multiple addresses for different things. For example, you might use one address for a job search and a different one for online shopping.
You can also create a new folder name which will be assigned to the new alias. That way, messages sent to those addresses can be kept in a separate folder.
Email aliases let you create completely different email addresses that you can use to receive email into your primary account without anyone knowing what your primary email address is.
You can create upto 5 aliases per year and 15 in total!
I must say its quite an innovative move and a rather useful feature!
Go here to create an email alias!