hmm, I read an item about SPTI and decided to try that: http://www.ste-home.de/cdrtools-spti/index-en.html
some quotes:
In meantime this is used by many burning applications and preferred by Microsoft
Advantages:
Cdrtools run without ASPI installation.
Alternative accessability, also with installed ASPI.
Possibly devices are supported, which are not recogniced by ASPI but available under Windows.
Device can be opened non SHARED, then simultaneous access (and disturbance) by other programs is not possible.
Disadvantages:
Administrator privileges necessary, can possibly be worked around, see EAC-FAQ (Q: I use Windows NT/2000, but EAC seems to have problems to store the options or get any SCSI response)
So this is not the same as the 'allocatecdroms' group policy option, that gives availability to the data on in a drive to locally logged on users: http://technet.microsoft.com/en-us/library/cc957388.aspx
But someone with access to the source code will know what the option in the setup actually does ;-)
At least all is working fine again as this my prefered burning software, haven't used nero or the like for more than 1,5 years!
kind regards and thanks for helping