|Don't rely on Registry Booster - if you have underlying problems then registry cleaners can make things worse.|
What exactly is the problem you're getting when trying to download AVG? Have you got any other sort of security program on your system? If you think that there may be a malware problem preventing you downloading AVG then try downloading & running Malwarebytes first - see if that goes ok & whether it finds anything.
The only registry cleaner I would ever recommend is the one that comes with CCleaner.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd