...I'd guess that you no longer have the D: drive you once had and that, due to the HDD replacement, D: was now the next open in sequence. When you inserted that new USB, the OS saw D: open and mounted your new USB there.
Insert the USB drive.
Right-click the "My Computer" icon on the desktop and then left click the "Manage" selection in the context menu that appeared, the Computer Management console will be displayed.
Be very careful here.
In the tree structure on the left select "Disk Management". A list of your disks will appear on the lower right. Generally, "Disk 0" will be mounted as "C:".
(It will look like this only with a tree structure on the left.)
Right-click the block with the drive letter of your USB in it. A context menu is displayed.
Select "Change Drive Letter and Paths...". The current drive letter will be shown.
Click "Change" and pick the letter you want and 'OK' out.
Best of luck. 
Edit history
Recommendations
0 members have recommended this reply (displayed in chronological order):
= new reply since forum marked as read