can't install error

Avast Free Antivirus / Premium Security
1

I couldn’t unistall avast a while back so I used revo uninstaller. It removed the program but still can’t reinstall
various errors come up

2

Revo isn’t advised for uninstalling any security based application, that should be left to the vendors own uninstall utility.

This assume you are using avast free as you didn’t mention the version you have:

  • Download the latest version of avast, 7.0.1473 http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe and save it to your HDD, somewhere you can find it again (if you didn’t save your last download). Use that when you reinstall.

  • Download the avast! Uninstall Utility, aswClear.exe find it here and save it to your HDD (it has uninstall tools for 5.x, 6.0.x and 7.0.x).

    1. Now uninstall avast! (using add remove programs, if you can’t do that start from the next step), reboot.- 2. run the avast! Uninstall Utility from safe mode, first for 6.x if previously installed and then for 7.0, once complete reboot into normal mode.- 3. install the latest version, reboot.
3

Revo is a BAD idea to uninstall antivirus and firewall. It is NOT good for programs that require a boot to uninstall.
You should follow: http://www.avast.com/uninstall-utility (in Windows Safe Mode if it does not work in normal way).
Check also http://www.appremover.com/