See this that I posted elsewhere and my answer when I realised what was causing my problems:
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One of my elderly home computers running XP has brewed up a fault. I normally run two widescreen monitors from the Nvidia 6200 card I installed some time ago at 1366 x 768, 60 Hz and has been running fine for years. What's happening now (and has a few times before the fault became permanent) is that boot-up looks fine initially. Usual BIOS stuff followed by the Windows start-up (animated squares) and the logo on the light blue screen, which appears to be at the normal correct resolution. However, just before the extended desktop should appear, the screens go blank with an "out of range" warning and the machine won't proceed any further, requiring a shut down with just one push of the power button. I know the meaning of the warning but, to me, it doesn't make sense. The machine will rustle up OK in safe mode, so I presume the graphics card is OK, running on a basic driver. I can't get into VGA mode from the "safe mode" menu screen to access the NVidia control panel as the I get a blue stop screen after selecting that which gives a paging error (conflict maybe?). I have downloaded and installed the latest appropriate driver in safe mode but no change from that. Numerous forums have an answer to right-click on the desktop in safe mode to access graphics properties and change either the resolution or refresh rate, which presumably can't be done in safe mode with only a basic driver loaded. This is sending me round in circles. I have also disabled every start-up item in MSCONFIG and still get the problem on boot-up. It seems to smack of driver or hardware to me but can anybody suggest a definitive way to diagnose?
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Well folks. You ain't gonna believe this but it was something to do with the latest Avast AV update! This needs widely circulating. I did their update on my Win 7 machine. Fine. No problems. I don't use Avast on my laptop or on another fourth elderly XP machine, AVG and Security Essentials being on those. Accepted the offered Avast update today on one of my other Win XP machines and straight after that it went into a cycle of re-booting/shutting down on start-up (not for the first time, I might add after an Avast so-called up-date) until I uninstalled Avast, using their utility in safe mode. A little light was shed and a bell rung in my befuddled head and, more on a hunch than anything else, I uninstalled Avast on the troublesome machine which had had Avast "updated" a few days ago. Sure enough, it booted up fine. No "out of range" error or blue stop screen! All this after tearing out the graphics card and going down goodness' knows how many paths to try and sort it out. It had me fooled completely. I can only assume that the problem was being caused by their boot-up scanner and some sort of conflict with the graphics card running two monitors to give the weird symptoms. Avast have managed to make a mess of their updates in the past and I and many others have had similar re-boot cycles which can be seen in a Google search but I think my problem may be unique. Avast need to get their house in order and get their act together regarding updates. It's a shame, because for a freebie, it's a very comprehensive AV program. It's also really annoying that I now have to re-arrange my many desk-top icons and install a different AV program. Couldn't restore position from the utility I have for this very job, as I had re-installed the Nvidia driver and control panel. Doh!
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I have had problems in the past following Avast updates, especially the cycling boot-up and I'm afraid this obscure problem may be the end of the line for me. A shame. Any comments?
