Avast installer doesn't play with the profiles directly, just thru legal win32 api. If anything destroyed the profile, Windows would be the first to blame. Such one-in-a-million accident doesn't prove anything though.
Oh, I'm more than willing to blame win32 (it's let me down more than a few times) ;-)
I've had this happen before, but it was due to my own un-wise modifications of some part of the system (most-notably, changing Permissions within the registry). I've a decent grasp of what I should, and should not, do to preserve a healthy system--my current install has lasted me well over a year, now, and things were <em>very</em> healthy.
My interest in purchasing the full product is dependent upon an analysis of this software, but that is all but nill until I can get some sound idea as to why this happened directly after a fresh install of a new piece of software.
If this happened now, it will (most-probably) happen again.
I have un-installed the software until I can narrow-down what may have produced this erroneous situation
My experience, in retrospect:
a) dl the software from avast.com (as a non-Administrator 'user').
b) logged-off user, and logged-on as Administrator
c) verified Full Rights to the entire registry and all fixed-disks
d) activated the .exe, and chose Custom Install (unnecessary I now realize, as I kept the defaults)
e) Accepted the License
f) Selected to activate the boot-time scan
g) Followed the Mail Scanner Wizard, chose Option #1 (I utilize Mozilla as my MUA, and send directly via SMTP via my ISP's Smarthost)
h) Rebooted, and let the boot-time scanner complete
i) Prior to log-on, my install of Kerio notified me that the Avast! software was attempting to establish a connection to 'somewhere' . . . pressed Deny about six times as I was unsure what this was all about (and I do not, in practice, allow unsolicited connections when I am not using my restricted, 'user' account)
j) Logged-in as my 'user' and boom!--my computer acted as if I had created a new account (Welcome Screen; default Desktop settings; email not working; etc.)
k) Explorer'ed to Documents and Settings to find that my user account still existed, yet an additional one had been created: 'user.COMPUTER_NAME' . . . I've seen this before, so I (thought I) knew what to do . . . logged-off user/logged-on administrator and deleted the user.COMPUTER_NAME account . . . log-off/log-on and the user.COMPUTER_NAME account was created again ;-\
l) Had to resort to drastics: delete both user and user.COMPUTER_NAME, log-on as user, and re-set my configuration manually/copy-over important info from a backup of the user account, etc.
m) Of note: my Administrator account was completely unchanged (thank-goodness)--verified by backup comparison
Any thoughts on where in this process I may have made a mis-step?