According to
http://download.microsoft.com/download/1/2/5/12538ba0-3d24-4f00-aab1-dd9ff4aacfc9/en_client_eula.pdf
Installation and use. You may:
(a) install and use a copy of the Software on one personal computer or other
device; and
(b) install an additional copy of the Software on a second, portable device
for the exclusive use of the primary user of the first copy of the Software.
It is generally assumed that this means one desktop and one laptop however
it doesn't specify that. You "cannot" put one copy on your laptop and one on
your spouse/friend/offspring/coworker's laptop. You must be primary user on
one and only user on the other.
