i have installed avast 5 free on 9 machines for myself and family members. a couple of xp sp3 and the rest vista home sp2 and vista professional sp2. all machines were upgraded by removing avast 4 and doing a clean install of avast 5. all machines also had at least 1 other anti-virus such as kaspersky, avira, or avg prior to avast. i always use revouninstaller and ccleaner for uninstalls. i have never used a vendor specific anti-virus uninstaller. using these tools, all my upgrades were painless and were helped by the quick install of avast 5 which amazed me (seemed faster than any anti-virus software i have installed). the install seemed really quick and lite on all machines but yet the new interface is much better (looks like it would take longer to install). i also wanted to say i really appreciate the new registration process which does not require retrieval of a key. i know there are a few little bugs to squash but i wanted to report that i and my family are loving the new software. after approximately 2 weeks of avast 5 the computers are running great including all networking (lan and internet). keep up the good work alwil and thank you for an excellent free anti-virus!
Welcome to avast forums.
Feel free to come back any time you need help or just to change experiences 8)