The key on the bottom of the laptop is probably the key for Windows XP,
the operating system, not the key for Office 2003, which is not the same
as Windows. You should have received a key for Office also. It may be
somewhere in your printed documentation.
Also, note, on my Toshiba A105, the key that you get is only for a
60-day trial; it stops working after 60 days and you have to buy a
"real" copy of the product (actually, I think you can just enter the key
from a "real" copy, but since Office does Product Activation, you will
have to either buy the product or buy a key (directly from Microsoft).
I do believe, however, that it accepts a "Students and Teachers" key.
You may have a true "full version" (not trial), or you may, like me,
have received only a 60-day trial version.