Also, ask friends and family if their work allows them to buy Microsoft products at a discounted price. I legally bought Office 2003 (includes everything and Microsoft Access) for $20. It retails for $500 (because of Microsoft Access). Ask around, legal Microsoft products are cheap if you know the right people.
Office 2003 gives you all of the office products at a great value compared to buying each individually. As the Full retail version is around 200$ at your local Compusa or Best Buy.
OEM products or Student/Teacher versions are a lot less. But you must be able to prove you are a Student or Teacher for the S/T versions.
I was able to purchase Windows XP and Office XP through my college for 10$ each.