I have to admit I would like to help but can't, because I am really confused by what you are saying. I am not sure what username and password you are referring to unless it is the username and password of the server computer. AC only needs usernames and passwords for internal security and not for connections.
Windows works well when set up well as JamesNT will tell you. XP is the best so far but WIN7 Pro is really good. Vista is horrible and you would be better off throwing it away.
The only way Vista and WIN7 Pro and XP can go into sleep mode is if it is set up that way. I don't use Vista, so I can't be sure. When I set up a new user or PC the FIRST thing I do is turn off all of the auto sleep and auto off modes for computers and monitors.
I would recommend not turning off any computer at all ever. Which means going into the Power section in Control Panel or under Screensaver and turning off all auto sleep modes.
There should never be ANY situation where you have to unplug and plug a computer back in. That is not a hard boot. A soft boot is the way it was intended using the software. A hard boot for when you are frozen is from the button on the front of a computer. One should never, nor ever turn off a computer by unplugging it. If you have to do that there is something seriously wrong with you computer.
I don't see where a driver or a windows update would cause this. Do you have System Restore? You can revert back to before an update. Those file are kept in Windows.
