We have several reports (more than a single report at least) about "unable to add adapter" problem on HP Z-series systems.
The problem is reproducible with the latest available SPTD driver version 1.62.
This problem became "known issue" for DAEMON Tools with SPTD 1.62 or earlier on HP Z-series.The problem is related to some specific incompatibility between SPTD driver and HP BIOS on Z-series.
We have contacted SPTD driver developers and reported this problem. SPTD dev. team will release soon new SPTD driver version which includes fix for this problem.