This is a Windows user rights issue, which is also clear from the fact the message does not contain any delphi style error codes
I had the same problem, even if bds.exe is run as administrator.
I looked into the bin folder, and alongside bds.exe is also bdsreg.exe.
The name gave me an idea, so I set it to run as administrator as well.
Now I could and can install my design-time packages.