If you read the End User Licence Agreement (available via the Help menu and
About Microsoft Word), it will tell you what you can do.  If the software
came with the Dell, it will probably tell you that it is only licensed for
use on that machine.  Otherwise, if it was a boxed retail copy, the licence
may allow you to install it on one desktop machine and one notebook, but it
depends on just what version of the software it is.