You write: - "My computer programmer friend says 'You mustn't have had word already' But I did! All my documents are written using word."
I ask: - Were all these documents written on the very same computer where your friend says 'You mustn't have had word already'? Maybe you had Word on another computer and wrote the documents on that machine but have forgotten?

The only other answer is that you have accidentally uninstalled Word. If you have the original Office 2010 CD and key then reinstall it.

Office 365 is a monthly subscription model of Office so be prepared to pay.

A free compatible option is to install LibreOffice and set it up to save in docx format. See Home | LibreOffice - Free Office Suite - Based on OpenOffice - Compatible with Microsoft


Good luck.