When I load up avast it says “avast! Simple User Interface” cannot load library from file: C:\Program Files\Alwil Software\Avast4\Aavm4h.dll
It won’t let me use most of the features on the interface. What should I do?
You can try a repair in control panel 
Add/remove program then click on add/remove avast.
Scroll down.
Choose repair then restart your computer to see if it works or else you can completely remove avast in safe mode then reinstall it.
Here is the removal tool:
http://www.avast.com/eng/avast-uninstall-utility.html
Thanks for your help!
Nice to be able to help you
More importantly let us know how you get on.
Welcome to the forums.