Well the windows error 00000005 is "Access is denied."
So it looks like you can't access either an avast folder or file and this is usually a permissions issue. What Operating System are you using? - if XP does your user account have administrator rights ?
Try a repair of avast. Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow. You need to be on-line to do this. Thought I doubt that this would work.
If that doesn't work try, uninstall, reboot, run the avast! Uninstall Utility,
find it here, install avast, reboot.
It would probably be best to download the latest version of avast and save it to your HDD, somewhere you can find it again. Use that when you reinstall.