Using device manager check your universal serial bus controllers and then USB Root Hub devices and on the power management tab make sure each hub is NOT allowing to tirne off device to save power. I have seen a upgrade and new install have some funny setting here causing me the same grief.

Why does Win 7 after a while often cease to automatically assign a drive letter to a usb external drive? When you connect the drive, it makes a tone that it recognizes the device, but the drive will only show up after you go to disk management and manually assign a drive letter. How do you fix this?

I think that the better way to fix a such problem is to proceed with a repair install for your windows 7 OS. http://www.sevenforums.com/tutorials/3413-repair-install.html This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.

Using device manager check your universal serial bus controllers and then USB Root Hub devices and on the power management tab make sure each hub is NOT allowing to tirne off device to save power. I have seen a upgrade and new install have some funny setting here causing me the same grief.

There are several possible reasons cause the partition table of the external hard drive cannot be read by Windows 7 properly. In this case if Windows 7 recognize that no drive letter for the drive, it will assign a drive letter. Most of this kind of issues will not occur if you reformat the drive in Windows 7 without any third party tools.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.