Upgrading to Office 2007 isn't a one-way street, which is just as well if you subsequently decide that you much preferred the way a particular feature operated in 2003 or Office XP.

For example, by default Office 2007 uses Open XML file formats. They won't be to everyone’s taste. And while you may not upgrade to Office 2007 immediately, you'll need to be able to open documents created by those who are. Here, we'll look at how to change the defaults back to the formats you're more familiar with and how to handle the new ones.

Open XML, which is the default formats for Word, Excel, and PowerPoint 2007, have great potential. Only trouble is, people using older versions of Office can't open them, while users of different versions of Office 2007 are given different options for opening and editing them.

Fortunately, it's easy to change back so they can be opened in Office 97-2003. Click the Office button on the top left, choose Options (beneath the list of recent documents) and Save in the left pane of the Options window. Then open the drop-down 'Save files in this format' menu, and choose the 97-2003 format.

You can't preserve everything in the older format: Word 2007’s SmartArt (stylish, editable chart graphics) can’t be saved in an editable manner within Word 97-2003 documents, but save the file as .docx and the SmartArt graphics will be preserved.

If you receive an Open XML document and don't have the appropriate 2007 Office application, those who have used Microsoft Update to keep their Office XP or 2003 application as current as possible should get a prompt to grab the relevant Compatibility Pack from Microsoft's site. Having installed this, you'll be able to open, edit and save Office 2007 XML files in Office 2003 or XP.

Versions of Office that predate Office 2003 probably won't recognise XML files at all. The Compatibility Pack is the only route to take here. With the Compatibility Pack installed, Word 2000 users can open, edit and save the .docx files directly. In Excel and PowerPoint 2000 you can't edit Open XML files directly, though you can open, view and save them to their respective older file format, then work on them. After finishing their work, save the file back to the Open XML format.

Older versions of Office and office apps made by anyone other than Microsoft can't open Open XML files at all. However, the Compatibility Pack lets you covert them to their Office 97 counterparts directly from Windows XP or Vista. Right-click a .docx, .xlsx, or .pptx file, click Save As and you'll get a window containing a field for the file name and a drop-down format menu showing the Office 97 format.

When you've edited and saved the file, you can right-click again to return to the 'Save as...' window; this time, the drop-down format menu will have the Open XML option for saving your file.

Should you need help finding the new locations of old Office 2003 tools and commands, Microsoft offers handy animated web-based guides to its new versions of Word, Excel and PowerPoint. Opening a guide brings up a page with the old 2003 interface. Click a pull-down menu command within that page to bring up the command's 2007 equivalent.

Click here to read our review of the Office 2007 suite.