I can confirm the difference between the SpeedUpMyPC scan and the Registry Booster scan is that the Registry Booster scan picks up, and resolves registry discrepancies which may cause errors or corruptions of programs.
SpeedUpMyPC on the other hand scans for unused and dormant files which can be safely removed. The files SpeedUpMyPC finds do not cause a problem other than that they take up disk space and some can contain personal data.
