I would check the video properties of your setup. It may have changed whether you intended to or not. Ckick on an empty space of your desktop display, and under "personalize" see if it appears OK. If not but the sample show Ok, them maybe the backgrd. color got changed, return it provided that is the problem. Don't try to correct to remove the problem, its to see if the problem arises there. As any changes here are the total video effect, so if one color is wrong then that suggests you have a failed "chroma" or color generator at fault, which is h/w based. A slo, you can change the ackgrd. display to another and see if the problem remains. You then either resolve that by swapping video cards or monitor. Another test is to use the DXDIAG at the start button. Type in that command and run the test, it should appear OK, if not it should clue you in. Try all this and check results. Of course, if you have a spare monitor or video card, use them to test w/o doing any changes check results.
If nothing seems to correct the problem and you don't think its h/w based. You can use Win7 restore feature. Find s restore point before the problem arose and click on it and see if that corrects the issue. Again, it is hoped no truw h/w fault is present, so if the problem remains after a restore, that again suggest some h/w fault. I hardly think any virus or similar would cause this problem at time in thinking.
I have a question, as my computer has either decided it hates me or has contracted a virus. When starting up my computer there is a red background instead of the normal black/gray and when I load up sites they are outlined with red pixels, as are the icons on my desktop. My computer was absolutely fine a couple hours ago. I have a Dell Inspiron with Windows 7 Home Premium, the model is M5030 and the system is about 4 years old(if that helps at all). I noticed that the red pixelation shows up mainly with the colors of blues, greens, black, and gray. I'm wondering whether I have a Virus or if maybe my monitor is messed up in some way. If anyone has any idea what this might be please let me know (running a Virus scan at the moment, to see if it finds anything)