Tech, guess what? Your advice works but ...
As we paid for AIS I decided to give it another chance before asking to get the money back.
At home, I ghosted my system partition to old IDE 20GB HDD. Unplugged other hard drives and rebooted. I find "clean installation advice" on many replies in the forum so I did as in your post because I do have Avast5 running. Uninstalled, safe mode, clean with avast cleaning utility, reboot and installed AIS in trial mode. Now what happen is really unusual - all my NIC adapters refused to work. I wanted to try wired and wireless, I had four network adapters in total (two wired, one wireless PCI card and one wireless on USB - everything working perfectly before AIS). All of them completely dead. No internet, no network, unable to login to the router. IP config shows no network adapters but all of them are visible (no X or ?) in Device Manager! Clicking on the icon of any NIC caused Dev. Manager to freeze. Clicking on the task bar icons shows nothing in the status. Pic 1 and 2 here:
http://tinyurl.com/yldqj2p Pic 3 is what I get when clicked on Repair button. Got no idea what was that all about - do you?
Apart from being cut off from the network computer was OK. And something else - the fdd drive issue. Every time I click on My Computer icon or going up in directory tree the floppy drive is checked and it takes about two, three seconds before I can do anything. Every beeping time! And, yes I do have autostart disabled for ALL drives.
I the mean time I had to do something and booted from my main HDD where I have Avast antivirus running and rest of the config is exactly the same as on the tested HDD. No problems at all!
I was about to give up but having old hdd fitted I wanted to try a FRESH Windows install. Another reason was that my Windows is quite old, over three years now and plenty of software been there.
After half an hour I find my XPSP2 installation disk! Hurray! I installed fresh system, all hardware drives and nothing else, not even Firefox!
Now time for AIS - installed, rebooted and guess what? Are you ready?
>>>>>> EVERYTHING WORKS PERFECTLY! <<<<<<
I mean every beeping thing, every device, every NIC, everything! The only problem is the floppy drive seek issue (very annoying!).
What I am going to do now? Well, I am not going to reformat and reinstall Windows on all my computers. No way! Free Antivirus works well with my current configuration. I see no reason to have AIS at the moment in this form and shape. There are definitely incompatibility problems but I am not going to investigate where in particular things are not right. AIS is a new product and very immature. I believe that developers will make it usable for 'every computer' just like Avast Antivirus is.
At the moment I would NOT recommend AIS. Sorry guys.
PS. Have a look at my 4 and 5 pic in the gallery (see tiny link above). Pic 5 is where setup stuck for good 30 mins (not happy). Pic 4 is the state of my Device manager after AIS has been removed. Looks terrible isn't it??