Question: I have a PC with two internal SATA 7,200 RPM harddisks: one is a 1 TB Western Digital, and the other is 750 GB. I’m copying data between them, but it seems to be very slow: for example, to copy 140 GB takes about 5 hours.
Does this seem reasonable?
Answer: In your comment on sblair’s answer you stated that:
?
however I believe that it is being zipped on the fly, then unzipped on the other disk.
This is the most likely cause as to your low speed.