I've had this problem a couple of weeks now. I have an Acer Aspire laptop with Vista SP2 installed. When I switch it on (battery in or out), it boots up, but sometimes it will send itself back to BIOS when on the screen with the green scroll bar along. It will do this sometimes once, sometimes twice, maybe 3 times, or not at all. The screen comes up that says windows has had a problem booting and offers the usual safe mode, safe mode with networking, last known good configuration, start normally. Last known good configuration doesn't make any difference, but if I select start normally it will work. Once windows has booted properly it works fine, there is no mention of any problems, and it will run for hours without problem. It is only before windows reaches the logon screen that it does this. I intend to do a repair but my disc is at university and I am at home in the meantime, so is there anything I can try in the meantime to rule other problems out?