Hello and welcome to JustAnswer,
Hitachi have not created an instruction manual for this external hard drive, so unfortunately no user guide exists for it.
You can transfer data from your internal hard drive to the external one by copying the data you wish to move and then pasting it to your chosen folder on the external drive.
If you need to free up additional space, you can use the Disk Cleanup tool to remove temporary Internet files, delete downloaded program files, remove Windows temporary files, such as error reports, delete installed programs that you no longer use, and remove unused restore points and shadow copies from System Restore, which will all help to free up extra space on your hard drive.
To use Disk Cleanup, click Start, click All Programs, click Accessories, click System Tools, and then click Disk Cleanup.
If you need any further information, just let me know, otherwise please click Accept if you are happy with my assistance today :)
The fact there is no manual is not helpful at all. The question now becomes how do I get the XL1000 out of the mirror image copy mode and allow me to move stuff to from my internal drive to the external drive without it backfeeding back to the internal drive. I have already cleaned the internal drive of unneeded files, defragged etc. and am still operating on the edge at reduced speed. No, I am not yet happy because I have learned nothing new.
There must be some software installed on your computer that is running the mirror image copying.
You will need to disable that program to stop the mirror image copy mode.