Although Cubase installed and works fine on my W7 desktop (I’m very happy with it and have been since VST24) the installation failed on my Vista laptop.
It said; ! module C:/Program Files (x86)/Steinberg/asio/asiodxfd.dll failed to register. HRESULT-2147024770. Contact your support personel.
Then I had the choice to quit the installation or to ignore.
I quit because cubase 6.0.3 works and has to keep working.
UAC = User Access Control. The bit that asks whether you’d like to carry on installing…etc.
Vista is not officially supported by Steinberg since about 1 years ago. Cubase is optimised for W7 but should run on Vista / XP machines.
Try reading the manual again and see if you can spot anything you might have missed.
If you need to reinstall take your t-i-m-e. That way you might see if anything happens (quickly) that you missed the last time.