I have been having some curious problems with a Win 7 Ultimate/SP 1 laptop. For a start the Desktop icons were constantly being rearranged and resized, that seems to have stopped for now, but I never found out what was going on. The other thing is that shortly after opening the first Web page in IE10 I'd get an Avast warning about a malicious Website. This could be the BBC, or Google, or Hotmail, whatever I happened to open first. After that there would be no further warnings. Avast support told me to boot into Safe Mode and run a full scan, and this is the crux of the matter. When I got the options, I chose 'Safe Mode with Networking.' A moment later a blue screen of text appears very briefly, much too brief to read anything, then a DOS screen appears, "Windows Error Recovery." "Windows has failed to start, a recent hardware or software change may be the cause." Startup repair can help diagnose and fix the problem." Only there have been no recent changes. "Launch Startup Repair" is the selected option. So I went with that.
Many minutes later the next message was: "Startup repair failed", and the option now was "Do you want to try system restore?" Seemed like a good idea. Many minutes later Windows re-booted, not in Safe Mode, and not to an earlier state, it was exactly as I had used it an hour earlier. So, tempting fate, I tried Safe Mode again. This time the "repair" ran for ages, but ended the same way. I used the power button to shut down, then re-booted, and everything looked normal. That much is good, but I still cannot get into Safe Mode. At Avast suggestion I used RKill, it found no problems. I used CCleaner, and Malawarebytes, no problems. Then I did a full Avast scan at boot, that found nothing. But something is wrong, and the trouble is it's is many months, maybe years, since I tried to use Safe Mode so I don't know how far back is far enough for an image to restore things to normal, or if I even have an image that is old enough.