Well I have XP Pro and no such problem.
What you are experiencing certainly isn't the norm.
I would suggest that you do a clean install of avast 9.0.2007 (not take a step back):
- Download the latest version of avast, 9.0.2007
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, avastclear.exe
find it here and save it to your HDD (it has uninstall tools for all versions).
- 1. Now uninstall avast! - using add remove programs, if you can't do that (as appears to be the case) start from the next step, reboot.
- 2. run the avast! Uninstall Utility, it will request it be run from safe mode (and will handle the boot into safe mode), Select the avast product it is you want to uninstall from the dropdown list (see image, click to expand), once complete reboot into normal mode.
- 3. install the latest version, reboot.
Note: The default install location for avast is C:\Program Files\AVAST Software\Avast.
Programs & Features, Uninstall/Change
Note 2. save the copy of avastclear.exe so it can be reused as some users are reporting that after running it, it is self-deleting.
EDIT: modified instructions to reflect new avastclear.exe, as it caters for product removal, so no multiple version specific removal required.