The file formats have changed from maya 7 to maya 2013.
First there is an "ignore version" flag in the open options. Make sure that is turned on. But there is a lot of changes that have been made from version 7 to maya 2013 so you still may be unable to open the scene directly.
You may be able to export to obj and then import the obj into maya 2013 but I do not know if rigging information is maintained in obj format.
I don't think there was an fbx exporter for maya 7, it's just to many version back. However, I believe that fbx would be a better bet for maintaining rigging info.
You may just be unable to transfer all the data from maya 7 to maya 2013. Sorry.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
Last edited by ctbram; 24-09-2012 at 05:39 PM.