uninstall and reinstall

How do I uninstall and re-install Avast? Tried it with windows add/remove program both in safe mode and in full mode.

Avast did a boot scan and upon reboot it stated that one of its files had been altered and then went to a black screen. I did several things including resetting to a previous working condition and finally got my PC going again. Since the original problem started with the altered file in avast I decided to uninstall the program and then re-install it.

While I was trying to my pc up in safe mode, I used the repair feature of Avast (before repair it showed around 450 Mb after repair it showed over 700Mb). When the system came up, I tried to uninstall it with windows add/delete program. Before uninstall It showed around 450Mb, would not uninstall and now shows 1,106 Mb.

Download Avast Uninstall Utility to your Desktop.
Download the correct version of Avast
Avast Free
Avast Pro
Avast Internet Security
Avast Premier
Disconnect from the net
Uninstall Avast via control panel

[]Run the uninstall tool and accept the reboot to safe mode
[
]Once complete reboot your system
[*]Reinstall Avast