Have you considered they alternatives to avast? Or just use widows defender. Hey, This seems to be a pretty common problem with avast, wether it's CPU, RAM, or disk usage. Depending on how often it samples it may be picking up burst activity as more constant.Still I'd uninstall and reboot/reinstall the latest version. What probably happening is avast is scanning files as you accessthem and it's picking that up. I would consider that normal to good if running a full system scan. It has determined you hard drive is capable of around 60MB/s and it's thinks it's being accessed as fast as it can be.
