Went into /control panel/Storage/Disk Manager/. Found the drive that does not
have drive letter assigned.
Tried to assign, the default was "H" which is the next letter of all used.
The message box said something like "This letter is used. Reset the letter anyway?"
Did it, but it was rejected.
My next option was to assign "I". the Response was "Invalid parameter".
Go into device manager and ensure that the device got installed correctly. Many times the problem is a bad driver that shows the device exists but wont let you access it. I am gonna suggest look for the most up to date driver.
Another suggestion would be to try more drive letters and see if for some reason they dont want you using the drive I. Let me know what you find out.