Hello Alvin,
Thank you for your earlier email to us at the Microsoft Store. I forgot to mention one more detail about Office 2010 that may help.
Suites of Office 2010 have different licencing options. On each product page, you will see two choices. The single PC license of Office 2010 is a 'Product Key Card' (PKC) license. A PKC licence is one time use only, so if you need to reinstall for any reason, this would not be possible. To obtain the software again, a new copy would need to be purchased.
The two or three installation license of Office 2010 is different. They are for a 'perpetual' licence, which allows you to transfer and activate the software from one computer to another, or on the same computer indefinitely. Your product key would need to be reset if it no longer works.
With any purchase of Office 2010, I recommend the second option because it has the future in mind. You would be able to reinstall it again if you need to.
Thank you for choosing the Microsoft Store,
Andrew G.
Microsoft Store Email Support