Check add/remove programs. Check c:\programfiles for an Alwil software folder. If present download and run the uninstall tool. Make sure the Alwil software folder is in the box.
Then your problem would appear to be with the Windows Security Center, XP has a known problem with the WSC either failing to detect the presence of an AV or firewall and also the problem you mention of not recognising the old AV is gone and a new one installed.
A sinthetyc explanation for switching to pc-cillin:
I got pc-cillin for free, as the customer of an online bank, and pc-cillin is suggested by the bank. Pc-cillin has also a firewall and i think i need a good firewall for security reasons.
The pc-cillin firewall on my pc has some performance issue when i do a search with google, so i’m not so sure i will keep it, may be i’ll switch again to avast, but I need a very good firewall protecting against phishing and things like that, and also it must not slow down my browser.
Well many forum members are using comodo firewall pro (which is free) and that would appear to work fine with avast.
There are many freeware firewalls such as, Comodo, PCTools Firewall Plus, Jetico, etc. - Zone Alarm free works fine with avast and has a reasonably friendly user interface, however, the free version is becoming bloated with trial ware and is also crippled as far as outbound protection goes In the Program Control, configuration area, the slider will only goes as far as Medium protection, if you want more you have to buy the Pro version.