This problem usually occurs in windows xp when a usb drive is usually plugged into a usb port but as some of the network permissions change overnight due to which the same drive that shown earlier as e: drive in windows explorer is not showing.

So now due to the network permission under E:\ and there is a conflict with the USb stick.

In short your removable drive or a normal usb drive is detected by the system but due to not being displayed in the windows explorer.

Lets see how you can figure out a simple solution to this problem.

1. Start >> Control Panel >> Administrative Tools >>Computer Management and now click on disk management.

2. Select the portable usb drive and right click on it and go to “change drive letter” then assign a new drive letter to it such as x,y,z to avoid any conflicts.

3. That’s it done! as soon as you assign a new drive letter i will show up in the windows explorer.