I just purchased Avast Internet Security and VPN. I also have Malwarebytes and C-Cleaner installed and want to know if either of these programs are still necessary or should I uninstall?
Malwarebytes has always been good for removing stuff from your PC if anything gets through AVAST but I have to say that apart from files retrospectively re-classed as PUPs (potentially unwanted progams) that has not happened for a long time. However it is still potentially useful to have a backup AV/AM tool, one which does not interfere with your main AV, to scan and recheck a file or whole system for peace of mind.
If it is set to run at startup I'd stop that, waste of resources, but I certainly wouldn't delete it. Use it as an on demand scanner.
CCleaner, despite AVAST's fumbling and messing around, almost ruining its well deserved good reputation, is still an important and highly useful, comprehensive maintenance and management tool. Other tool-sets can do what it does but few do it as well and as reliably. It also has, like other Piriform originated software, IMHO, a one of the best designed, noob friendly, unintimidating GUIs you'll find.