The retail version of Home and Student edition of Office 2007 allows three installs. You only need two. That wouldn't be a problem.
An upgrade, of course, replaces the license for the upgraded product. If you want to use both, you need two licenses.
I have a licensed Office 2003 Standard installed on one computer. I am about to purchase a new laptop and will purchase Office 2007 Standard upgrade version at the same time. Does anyone know if I can install Office 2007 on my new machine (via an upgrade CD) and leave Office 2003 on my old computer (which will become a spare machine at my house)? I guess I am trying to figure out if (a) by using my old Office 2003 as the basis for a 2007 upgrade, does that wipe out my old Office 2003 license? and (b) if (a) is yes, since I only have it installed on one machine now, could I just install 2007 on my old machine too? I would like for the old machine to still have Office as a backup when I don't bring my new laptop home from the office (and just use a flash drive).
Thanks for any insights.