Providing that you only use one at any time, then Yes. If it was a business
computer and someone uses it whilst you were 'mobile', then NO. But
presumably for a home PC, no one will be using whilst you are 'mobile' so it
is OK.
For the Home and Student Edition of Office 2007, you can use it on
three computers per household for persons who reside there, but not for
any commerical use.
You can find the license at:
Office Button | Word Options | Resources | About
Then click on the "View the Microsoft License Terms". Check Section
2(a).