I cannot open an email attachment (of a .docx file) with Adobe Reader

I received an email in Windows Live Mail with an email attachment. Although it says it's a .docx file, Adobe Reader gave an error message. Adobe Reader could not open the file because either it's not a supported file type or because the file has been damaged (for example, if it was sent as an email attachment and wasn't properly decoded). I've tried checking the default programs to see if .docx was set up to be decoded by Microsoft Office Client Virtualization Handler. It is. How do I set this email attachment to open?