|The Xcopy that's built into XP is an old legacy program and it doesn't "understand" file extensions with more than 3 characters. |
You could use that Xcopy if you re-name all files with the *.docx file extensions to something custom other than *.doc so you can identify which ones they are easily, then re-name them to *.docx on the destination computer,
- or - you could use something else newer to copy the files, such as copy in XP itself (if you use it in Windows - Control Panel - Folder Options - View - change default settings to Show hidden files and folders - Show protected operating system files).
- the latest version of XXcopy, a third party modern version of Xcopy, was released in 2012:
A freeware version of it is available: