Haven't considered this since I have been using EAC with SPTI for ages. The funny thing is, EAC does work with the internal IDE drive.
Using other software (used Windows Media player for that job), the external drive (this is a 5,25" half height unit with its own power supply- incase anyone asks) works fine.
I usually run application software as ordinary user without admin permissions. For troubleshooting, I tried "run as admin", but this did not help. EAC does not detect this drive.