Advanced Format HDDs, USB enclosures and Windows / Linux compatibility

I believe the issue that you are having is that there is simply NO partitioning scheme on the disk.

What you may not realise is that Linux will allow you to treat the whole disk as a block device - ie a single big partition - and all the information you've provided seems to point to this kind of setup. I believe Windows will not support a raw block device.

The typical way to fix this problem would be to copy the data elsewhere, partition and then format the disk (using FAT or NTFS or some kind of file system both Windows and Linux can read) and then copying the data back on. If it is possible to do this whole process without actually moving the data off the disk, its high risk, and you really should back up the data first anyway, putting you back to square one.