External hard drive shown as local drive

External hard drive shown as local drive

I have an external USB hard drive (about two months now) to which I
assigned drive letter T:. However, each time I start up my PC, the drive
is shown as local drive (K:) and I'm missing my data. When I disconnect
the USB and re-connect it, the drive is shown correctly again.
Can I fix this behavior?
Specs:
Hard drive: Toshiba STOR.E Canvio 3TB
OS: Windows 7 x64
Notes:
I tried using different USB ports, all have same behavior.
The drive has been formatted multiple times (file system NTFS).
I checked the hard disk in the disk management tool of Windows (after
re-connecting the USB) and that shows that the drive has one partition.
I cannot check how the hard drive behaves with other PC's, because I don't
have another PC with Windows 7 (only Windows 8).