How to reinstall Microsoft office 2007 that came preinstalled but lost due to Recovery

My insprion 15  5558 ran into bluescreen error again and again and even my nvidia display adaptor didn't respond or reinstall...and window crashes down..even if i ran diagnostics using Dell SupportAssist so.. to get it fix ...i used dell backup and recovery to factory reset my insprion ..but every thing was ok except i lost MS Office 2007 enterprise that came preinstalled...and was activated already...Also MS Office 2013 was also preinstalled but it was a trial so..i wan't to know How to get MS Office 2007 and reinstall it.