Error fixers are generally always registry cleaning tools, and they can vary from disastrous to great. ALWAYS read as many reviews as you can before even trying one, let alone trusting one.
The reg tools I include in my arsenal are all built into tools that do various things. I tend to steer away from the tools that only do reg cleaning. Not that there aren't some good ones, but there are a multitude of bad stand alone reg tools that can really mess up your PC.
The reason there's so many suspect stand alone reg tools is simple. A lot of people don't know much about their PC's registry, it scares the crap out of them, esp when they read guides that tell you to stay away from it. That makes it easy for tons of people to crank out reg tools and scare you into thinking you need their's to keep your PC running in top shape.
That said, I wouldn't necessarily trust what MS says either, that the registry self repairs and doesn't need special cleaning tools. It's easy to see from MS's OS versions over the years that Windows is very vulnerable to everything from severe fragmentation to clutter from redundant file build-up. Believing a Windows reg is self repairing is like believing Alan Greenspan claiming the stock market would automatically stabilize from the bank derivative scams.
Tools I use that include reg cleaners are...
Auslogics BoostSpeed
CCleaner
Glary Utilities
Revo Uninstaller
Revo does not clean you reg in general, but it's great for thoroughly removing a given program or game by looking for any leftover bits it finds in your registry.
As far as AVG goes, it's improved over the years, but I still think Avast is the better option.
i appreciate it thanks!