Welcome to Android Central! Are you using Windows Explorer to drag and drop? Have you tried a different USB cable? Can you transfer other files without difficulty?
How big is the file? If it's bigger than 4 GB, it might exceed the maximum filesize allowed by the system on the 2012 N7. Even though it should be using ext4 (which technically allows a 1 TB maximum filesize), my understanding is that the N7 is still limited to 4 GB files (which is the max for FAT32).
Thanks B Diddy! I've been trying to copy the files across using the "View Files" option from the automatic prompt that comes up when connecting the Nexus, so I guess that's Windows Explorer. Although the window is always blank with no folders, I would have expected to see folders in there.
I haven't tried a different USB cable (I don't think I have a spare one), although it is the one which came with the Nexus, and the Nexus is recognized when I connect it which would suggest that the cable works. I haven't tried transferring any other files yet, as it's a brand new device (I've been able to download one or two apps two it through WiFi).
The files aren't huge, they are all around 1.5GB each, and the largest is just under 1.7GB. Only 2GB of the Nexus is currently used up.
I did wonder if there might be a file transfer utility that I could download which might help to recognize the Nexus?
I also went here:
https://www.asus.com/support/faq/1004005
and tried downloading and installing the USD driver but it didn't seem to help. I also tried updating the driver as per those instructions but it didn't work as it said that the latest drivers were installed.