Win7 64 wont start on a Sony Vaio. It will sometimes get to the desktop and seconds later it shuts down. No logout, just a black screen total shutoff. when restarted the black screen popped up again but this time it was with the message "windows failed to start" and the options were either "launch startup repair" or start windows normally. I chose "launch startup repair". The startup again goes to the immediate shutdown, more quickly each time it is tried. I have gotten into safe mode and performed a memory and disk check which were ok. It seems to go farther into the startup after it has been shutdown for a while. It is still under warranty.