Thanks to everyone for the help and suggestions.
EmuTOS works fine for me so far so I guess I'll stick with that.
But in order to verify/falsify this issue, I checked out various TOS versions.
TOS104UK, TOS104US, TOS104DE, TOS106US, TOS106DE,TOS162US,TOS162DE:
HDimage from Hatari homepage detected and automounted as C, Cartridge as c, Gemdos drive not automounted and option to mount drive greyed out in options.
TOS205DE, TOS205IT,TOS205US,TOS206UK:
HDimage from Hatari homepage detected and automounted as C, cartridge as c , Gemdos drive not automounted but mountable via options. If mounted via options--> install devices, drive mounted as device G but also 4 other devices (Device c, D, E, F - no idea what they are).
So it does seem to work, but only from TOS205 onward (albeit with a bit clutter on the desktop

).
My config:
Win7 64, Hatari 1.80 64, HD image from Hatari site mounted as ACSI HD image, Gemdosdrive write protection off, no booting from HD, machine type (ST or STE) autoselected by Hatari after selecting TOS image.
Anyway, for me all of that is not really a problem.
Hatari works great for my purposes. Kudos at the developers.

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