Hello PBNkapamilya and welcome to the forum.
We have assisted many people here with their installs, upgrades, uninstalls, malware, and many other issues. It has been my experience having XP that after installing Avast that you need to reboot the machine at least once (sometimes twice). It gets the registries and drivers all settled in and makes for a happy machine.
Once this is done, then open your Avast GUI (the orange ball on the bottom tool bar), and check to see if those missing items are now there. If not after one boot, then reboot a second time.
If you still have problems, then the AVG removal may have left remnants (left overs), which will cause conflicts with any security software such as Avast. If you already ran the AVG removal and tried the Avast repair as mentioned by the previous poster and you are still having problems, the next step would be to uninstall and do a
clean install of Avast:
1. Save a copy of newest version of Avast (5.0.594) for the version you need and save it to your HDD:
Free –
http://files.avast.com/iavs5x/setup_av_free.exe 2. Download the Avast Uninstall Utility, aswClear5.exe
http://www.avast.com/uninstall-utility and save it to your HDD.
3. Disconnect from the Internet at this time.
4. Uninstall Avast through "Add/Remove Programs" through Control Panel if possible.
5. Boot into
Safe Mode (hit F8 repeatedly) and run the Avast Uninstall Tool.
6.
Reboot twice.
7. Clean your computer up (clean up cache, temporary Internet files, etc.).
8. Install the newest version of Avast and
reboot.
9. Get Internet access and update Avast definitions.
10. Register your copy or add the license key for
Free -
http://www.avast.com/registration-free-antivirus.php.
Please let us know how things work out for you. We are here 24/7 for assistance. Thank you.