Provided that the firmware supports the HPA (Host Protected Area) feature set, you could use a tool such as HDAT2 to cut the capacity of your drive. You would limit its capacity to the maximum LBA that can be addressed with 28 bits. This change is not permanent, so you can undo it at a later time.
The procedure for creating a HPA is explained on page 5 of the HDAT2 Cook Book.
HDAT2/CBL Hard Disk Repair Utility:
http://www.hdat2.com
http://www.hdat2.com/hdat2_faq.html
http://www.hdat2.com/files/cookbook_v11.pdf
