Preferred File Format for Attachments
Refer to the assignment or activity requirements in your Moodle course to determine what type of file you are required to submit.
To prevent the problems that can result from software and version incompatibilities (e.g. between Office 2003 and Office 2007), save and send all of your Moodle attachments for your course(s) as .rtf or .doc or .xls or .ppt.
Do not submit files saved as in the Office 2007 default format (.docx, or .xlsx, or .pptx).