As long as you have a legitimate copy of Microsoft Office, you should be able to reinstall it after you perform a system restore on your laptop or PC. Here’s how to keep Office when you reset your laptop or PC.
Restoring your laptop or PC to factory settings is something you might want to do if it’s full of malware or viruses, or simply because you want to sell it on or give it away. Here's how to restore a PC with a hidden partition
However, this process will wipe not only all your files – music, photos, videos and documents – but also any programs you installed after getting the laptop out of its original box.
The first application most people install is Microsoft Office: it isn’t part of Windows as many people mistakenly believe. Word, Excel, PowerPoint and other applications are all part of Office, so will be lost unless they were already installed when you first got your PC. See also: Speedy shortcuts for Microsoft Word
In order to restore your laptop and keep Microsoft Office, you will need at least the original product key, also known as an activation code or serial number. It’s usually 25 digits long.
If neither of these programs recover your Office key, it's worth trying Recover Keys which can extract keys for over 6,500 programs. It isn't free, but you can get 20 percent of the standard price of £19.95 by using this special discount code for PC Advisor readers: PCADM20RK
Be sure to do this BEFORE you restore your laptop, of course.
The second thing you need is the installation media, which is typically a CD or DVD. However, if you’ve lost this, or your laptop doesn’t have an optical drive, you’ll need to obtain the files another way.
Fortunately, Microsoft makes this relatively easy. So, to start with, head to office.microsoft.com/backup and click on the relevant download link. You’ll be asked to enter your 25-digit product key to verify you own Office.
If you had Office 2007, you can try this link
Or for Office 2010, try this link