Can I upgrade from Office SharePoint Server 2007 to SharePoint Server 2013?
Not directly, but you can do what we call a “double-hop” database attach to upgrade from Office SharePoint Server 2007 to SharePoint Server 2010, and then from SharePoint Server 2010 to SharePoint Server 2013. Back up your content databases from 2007, set up a small, temporary farm with SharePoint 2010 (you can even use virtual servers if you don’t have space, and a trial version), and attach and upgrade them to 2010 there. Then, set up your destination 2013 farm, back up the 2010 databases, and attach and upgrade them to SharePoint 2013.
This upgrade path also applies to upgrading from Windows SharePoint Services 3.0 to SharePoint Foundation 2013 – you must upgrade to SharePoint Foundation 2010 before you go to SharePoint Foundation 2013.
I don’t have an article about this “double-hop” upgrade path just yet, but I am working on getting one out there as soon as I can.