With all the back and forth of changed drive letters it could have an impact on the avast installation.
Try a repair of avast:
XP - Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button and scroll down to Repair, click next and follow.
You may need to reboot after the repair.
If that doesn’t resolve it you may need to reinstall avast, a clean reinstall might be best:
-
Download the latest version of avast, 6.0.1125 http://files.avast.com/iavs5x/setup_av_free.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 both 5.x and 6.0.x).
-
- 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 5.x if previously installed and then for 6.0, once complete reboot into normal mode.- 3. install the latest version, reboot.