If you are facing issues in transferring data from and to external hard disk (USB) using a Windows7 system, then most likely the solution given here should work for you.

My System Config

1. Windows7 Professional, 64 bit
2. Lenovo Thinkpad T520, 50 GB HD, 4 GB RAM, Intel i7 2.2 GHz

Symptoms

• External hard disk to and fro transfer rates were extremely slow

Debugging

1. The problem was not with the USB Cable
2. I was able to replicate the problem with both my Seagate Freeagent 750 GB as well with WD Elements 1 TB drive
3. The copy from Local disk (C:\) to Local disk (C:\) also became very slow at these times, though better than the external HD one
4. The problem was not there EVEN on my old laptop -Windows XP, 100 GB HDD, 2 GB RAM, HP      6910p 

What are the things that I found on net that did not work?

• Note that the disabling of the BIT (Background Intelligent Transfer) Service or changing the Policy of drive  to "optimize the performance" didn't work for me.

The following didn't do any wonders for me :-

1. Open "My Computer" or "Computer" from your (Start) Menu or Button
2. Right-click the external Hard disk drive from the list and select "properties"
3. Click the "Hardware" tab
4. Highlight the drive your having problems with from the drive list and click on "Properties"
5. Click on the “Policies” tab
6. You will see two radio buttons - "Optimize for quick removal" and "optimize for performance"
7. If not selected, select "Optimize for performance" and click on "OK". If running Vista or Windows 7 also check "enable write caching on the disk"
8. Click on "OK" and exit

Nor did the following work for me :-

1. Go to Control panel

2. System and Maintenance

3. Administrative tools

4. Run services shortcut

5. Stop and disable the BIT (Background Intelligent Transfer) Service

These are given here:

http://www.howtogeek.com/forum/topic/external-hard-drive-is-reallly-slow

But I reached to the eventual solution via a link from here via a post by "noiox8"

What worked is the solution given here courtesy Peter Bromberg. Thanks a ton Peter!

http://www.eggheadcafe.com/tutorials/windows-7/69610eb9-5429-48d8-a00a-e0547fd30ff4/how-to-make-windows-7-lean-and-mean.aspx

Turn off Remote Differential Compression

Remote Differential Compression measures the changes in files over a network to transfer deltas with minimal bandwidth rather than transferring an entire file that has previously been moved. Because it constantly checks for file changes, this service can hinder system performance.

To disable this service:

1.      Open windows7 search box

2.     Search for “Turn Windows features on and off”

3.      Scroll down and uncheck Remote Differential Compression

This eventually worked for me.Quirks of windows!

Hope you find this useful and it works for you if you face this issue.

\Vikram