All your documents created using Office 2003 or any office 2003 document are safe. All of them can be open under Office 2007.
FYI: To open a Office 2007 document under office 2003 you have to use a the compatibility pack
http://www.microsoft.com/downloads/details.aspx?FamilyId=941B3470-3AE9-4AEE-8F43-C6BB74CD1466&displaylang=en
To install your office 2007 on your laptop, depends on your office version and license. I am sure that:
• Office Home and Student 2007 Retail License Terms allow for installation on three devices.
• OEM License Terms limit the installation to the device on which the software was pre-installed, I am not sure about using it also on a portable device.
• A RETAIL license can be used on a desktop (licensed device) and also installed on a portable device (laptop is included) if it is use by the single primary user
To be sure check your license and verify your License Terms for your product. For this, follow these steps:
• Open Access, Excel, Powerpoint or Word
• Click the Office Button
• Click the Options button for the Product
• Click Resources and then Click About
• Click View the Microsoft Software License Terms
Hope this help