WinXP Pro SP3++ 9.0.2006 free was ok, save for a permenent "not all shields are active" status when they were.
It maybe worth noting that it was intalled in Program Files/Alwil Software - not my choice, probably historical.
A straight update to 9.0.2008 was a disaster: bootup stopped with wallpaper but no icons, start bar, or any funtionality except cntl-alt-delete.
Safe mode Control Panel/Add Remove Programs produced an Avast Uninstaller/Repairer which was too big for the display, and even when the Continue button was juggled into partial view it did nothing.
Unfortunately my copy of avastclear.exe was on a different PC, however I cracked it by dumping the whole Alwil folder in RecyleBin after which it rebooted ok in normal mode and I was able to retrieve avastclear, restore the Alwil folder, and then run the clearance in Safe Mode. Following this, a re-install of 9.0.2006 was a complete success - I am not in a hurry to try 2008 again.
DEEPSCREEN is a PAIN - I maintain a suite of 20 programs and have had to switch it off.
