I have Office 2007, at home, Office 2003, at work, and also OpenOffice.org at home. I found that I needed to open MS Access 2007 files, with OpenOffice.org.
Because Windows XP (and I think Vista too) does not have the Access 2007 database engine installed, by default -- even if one has Access 2007 installed, as I do -- one has to download and install the newer database engine in order to open Access 2007 files with OpenOffice.org.
You can get it here: http://www.microsoft.com/downloads/details.aspx?FamilyID=7554F536-8C28-4598-9B72-EF94E038C891&displaylang=en
Search this blog for prior occurrences of 'OpenOffice' to read my other postings related to this totally free Office-compatible suite.