I use CCleaner too, and I also use from time to time Auslogics BootSpeed. The latter has a great file and registry defrag (which you can download separately for free). These defraggers are really fast (faster than Vistas defragger). The Auslogics file cleaner works the same as CCleaner, but its Registry cleaner gets at some problems that CCleaner doesnt.
For security, I use AVG Free and ZoneAlarm free, and I have had no problems at all with any virus or security issues.
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