with my computer, if I am moving large files, while transferring, I see it slowing down, sometimes to 30 Mbs, you might try this, Start, Accessories, Run(right click, run as admin), fsutil behavior query memoryusage, should return a =0, type fsutil behavior set memoryusage 2, reboot the computer let us know if it helps
You changed the page file sharing to 2, which is the max, the green drives are slower( I have a 1 TB WD Green new style drive 1024 clusters, it runs very cool but it is slower than my 1.5TB Seagate, which is VERY hot, I had to put a fan on it to cool it down) but the rest of the slowness is from the drive and I am not sure if there is any thing more that you can do, as a second thought, do you have the drive partitioned? the drives in my computer that I use everyday are partitioned in 100 to 150G partitions, the 1 and 1.5 TB drives I use for archiving, so they are not partitioned, with smaller partitions the OS does not have to look at all the files in the drive when you request them
Reading and writing to a mechanical drive at the same time is going to slow it down no matter what you do. The head can only work on one thing at a time and when its rapidly switching back and fourth it will bottleneck. The greens drive weren't made for performance either, they were made to be always on and remain cool, and quiet.