Try <a href=”http://www.uwe-sieber.de/usbdlm_e.html”>USBDLM V4.2.4 – USB Drive Letter Manager for Windows 2000, XP, Server 2003 and Vista</a>
Have you tried this process? (More info can be found <a href=”http://www.petri.co.il/control-usb-drive-letter-assignment-in-windows.htm”>here</a>)
To work around this issue if the new volume appears in Disk Management, specify a different drive letter for the new device or volume. To do this, follow these steps:
1. Right-click My Computer, and then click Manage.
2. Under Computer Management (Local), click Disk Management.
3. In the list of drives in the right pane, right-click the new drive and then click Change Drive Letter and Path(s).
4. Click Change, and in the drop-down box, select a drive letter for the new drive that is not assigned to a mapped network drive.
5. Click OK, and then click OK again.
There might be a default settings of your computer system or Operating Systems which always assign a certain drive letter for any external storage devices detected in your computer. You have to carefully check that configuration and try to change the drive letter.