OpenOffice is a great substitute.
A piece of advice though never buy a Microsoft product at full price you can nearly always get good deals on their website.
If you are any kind of college student you can get their full office 2007 suite for about £39/$59 at
http://www.microsoft.com/student/dis...s/default.aspx. They have this offer for various countries.
They had a special offer on in December on their website where it was available for £89 so its always worth rechecking the site on a regular basis. Office 2007 is an incredible suite and really does save time with it's enhanced functionality.