Although you can usually click through most software license agreements with little consequence, you should probably skim Microsoft's terms before spending $140 to $400 on a retail copy of Office 2013 as two key parts have changed from previous versions of the suite. If you purchased a retail edition of Office 2010, the end-user license agreement (EULA) permits you to install the software on up to two devices at once (a desktop and a laptop) and if you retire one or both of those systems, your license is transferable to new machines. Neither of those permissions exist with Office 2013. Microsoft's updated EULA only lets you install the boxed editions on one computer, and only that computer -- forever. If I understand the terms right (and they seem pretty clear), you aren't allowed to transfer your license:

Can I transfer the software to another computer or user? You may not transfer the software to another computer or user. You may transfer the software directly to a third party only as installed on the licensed computer, with the Certificate of Authenticity label and this agreement. Before the transfer, that party must agree that this agreement applies to the transfer and use of the software. You may not retain any copies.

The updated EULA essentially demotes retail builds to OEM status, which seems comically restrictive given the price of Office -- especially the Professional edition. Are you really supposed to spend another $400 on a new copy if, say, your computer croaks?