It sounds like your installation is corrupt and this may have meant other problems in your use. Are these what made you decide to uninstall ?
In Add remove programs, there is a Change/Remove button and that should open another window with other options, Repair, etc. so that part is corrupt, so there are likely to be other issues.
If the reason you wish to uninstall are problems with the current install, try this:
Download the latest version of avast
http://www.avast.com/eng/download-avast-home.html and save it to your HDD, somewhere you can find it again. Use that when you reinstall. Ensure that you scroll down and select the avast direct download link for the English version and not Cnet as that is for an on-line installation (not what you want to do). - Direct download for avast Home, English version,
http://files.avast.com/iavs4pro/setupeng.exe.
Download the avast! Uninstall Utility,
find it here and save it to your HDD.
- 1. Now uninstall (using add remove programs, if you can't do that start from the next step), reboot.
- 2. run the avast! Uninstall Utility, reboot. If step 1 failed it may be necessary to run this from safe mode, once complete reboot into normal mode.
- 3. install the latest version, reboot.