You might be knowing that Office 2007 saves documents in different format than its previous versions (.docx, .xlsx, .pptx etc.) but you might be willing to share your documents with people who haven’t it installed or you might have documents which are in Office 2007 format and you haven’t it installed on your computer.
There exists only one online service which lets you convert any Office 2007 document to the formats compatible with previous versions – Zamzar. You can use Zamzar to convert files in different formats. It is a four step procedure to convert the files online.
PS: Also there is compatibility pack which was released by Microsoft that allows you to read Office 2007 files in previous versions of office.