If you have Windows XP, then log in to Windows as Administrator, start
an Office program, accept the EULA, close the Office program, log out of
Windows as Administrator, and log back in to Windows using your normal
user profile.
If you have Windows Vista, then right-click on an Office program
shortcut, choose to run the Office program as Administrator, accept the
EULA, close the Office program, and then start the Office program normally.
If the previous suggestion doesn't help, then see
http://support.microsoft.com/?kbid=884202 "You must accept the Office
End User License Agreement every time that you start an Office program".