This IS AN EXERCISE in STRAW GRABBING !!!
I KNOW this might sound stupid, but I think the first thing I would do IF the thing boots up into Windows, would be to place my pointer in the middle of my desktop, right click and see if my “display properties” dialog box opens and is readable. Then I would click on “Appearance” then “Advanced Appearance” and make sure the color schemes are whatever color back ground, and a contrasting color forthe text and stuff. I mean this is a long shot, otherwise it sounds as though you are going to have to bite the bullet and start all over with a fresh install of Windows. There IS a possibility that when you downloaded AVG free, you somehow got on a hacker site. THAT happens some times.
For those who MIGHT not know AVG free is at http://www.free.avg.com, and then follow the instructions.
I DO find it interesting that DrWatson left a log when nothing else shows up. That in itself leaves out a lot of “other guesses!”