Maximum PC

I hav two equal WD Passport 1TB HDDs USB 3.0 and I cannot assign them their individual drive letter. No mater which one I plug in it always reads E: and I cannot have them running at the same time on my laptop. Tried mini Tool Partition Wizard to no avail. Even went as far as to change the serial numbers for each drive but no luck. What am I missing?

Try going through Disk Administrator and assigning drive letters in that manner... Right-click 'Computer,' >> Manage >> Disk Administrator.

Have both drives plugged in at the same time.