Computer not working after avast! Installation?

After my computer being slow and choppy on YouTube, I decided to download a free antivirus. I downloaded avast! Thefree version, and after redrafting my computer "to allow settings to apply" my computer turned to poop. It will start up and log onto my account, and that's about it. While it's still starting up if I click control panel or something, it will come up, not completely load, then say "not responding" regardless as to what application it is. As I'm typing this on my iPhone, it is frozen on the desktop, with the loading icon. I'm seriously stuck and have no idea what to do. Can someone please help!

After you download an antivirus, it will keep scanning in the background, especially the first time… It could take hours… Even after than, an antivirus program only slows your computer down, because it checks each file before it opens… If your computer is already slow, it will be even slower with more programs working in the background. Be prepared to let the antivirus program do its job… Like start it up before you go to bed and let it keep working… Or just uninstall it altogether.

Your computer might be suffering from different problems to improve its performance you should:

- Scan your computer with an antivirus
- Apply De-fragmentation on your system
- Delete all temporary files
- Run disc clean up

Specially De-frag your registry, Because sometimes in removing any program from the system would remove essential files from it, that's why your system start freezing after sometime, use Reginout registry manager to get rid of these problems.