I suspect what's happened, is that he inserted his W7 Home Premium upgrade disk into the DVDRom, which activated autorun, when he said ok, it started the instalation. Because he was running W7 RC, which is Ultimate, that is why Ultimate upgrade was installed.
"Can I shut down and still keep my current configuration data etc until I can install home premium? "
No, at this time your only option is to reinstall from the beggining.
Backup all your files and settings to anther drive or dvd, using W& Easy Transfer Wizard.
Then either reinstall the W7 RC using the original key, or install your W7 Home Premium with the supplied key.
Be sure to select the correct version that you have a key for.