Thats really weird, if its not an issue with the moniter itself, it could be something to do with graphics drivers or maybe even your graphics card itself (could be nearing the end of its days). Although there wouild be some kind of integrated graphics thing bundled into the computer as well so thats probably not it. Maybe its something to do with your windows install corrupting, but these are all genneral stabs in the dark and I'm probably nowhere close to the actual problem. I vaguely recall seeing something that looked like this years ago with windows xp though... Ill have a think about it and hopefully have something more accurate to help you with.
Also, have you dried going into your display settings for windows and checking that the font and text size are as they should be? I think theres an option for smooth text or perhaps its something to do with the Aero UI wondows vista and 7 are so fond of. Does the problem still happen if you switch to the windows classic view? If the text is only buggering up in some places its probably not an issue with resolution or refresh rate on your moniter... and also probably not a hardware thing like I said above.