try these steps :
1)try upgrading your ram. this will help.
2)defragment your drives regularly.
3)if you can spend some money buy tera copy software,it's really nice.

You could also try TeraCopy which has been designed with the above in mind.
http://www.codesector.com/teracopy.php

Thanks for the tip!

How often should you defrag your hard drives? Can external hard drives be defragmented as well? I have a 1 TB MyBook.

Large files normally cause more fragmentation in my oppinion and also slow down the hard drive more.
I would recommend using MyDefrag or and Automated Defragger like Smart Defrag. There both free )

I have heard some people say you should defrag every month, I guess it depends on how much you use your computer though.

Tera copy soft ware is really nice. You can download it and can reduce your copy time. Otherwise you have given very good tips to reduce the time to copy large files.