So my parents computer is running very very slow, and I'm certain that most of the issues are due to downloads on the guest account.

I've used RKill and then ran Malwarebytes, Rougekiller, ADWCleaner, Malwarebytes junk remover tool and Spybot search destroy. Booting up is very fast but after logging in it takes a long long time until you can actually do anything (and the startup programs is only limited to avast and ccleaner).

So after you can actually open applications, it usually freezes up within 30 seconds to a minute for long enough to where I just reboot the computer. And trying took into guest on safe mode just brings this message.

Windows could not connect to the SENS service.

What do?