Howtogeek posted a guide about tweaking ClearType in Windows 7

Would you like to make your fonts look nicer in Windows 7?  Windows 7 lets you easily turn ClearType on or off and tweak it to work best for your monitor, so let?s see how to make ClearType render fonts the way you want.

What is ClearType?
ClearType is a font smoothing technology introduced with Windows XP.  It is designed to smooth the fonts on your screen with subpixel rendering to look great on LCD screens.  Fonts can easily look jagged and pixelated on LCD screens since they have fixed pixels; this was not a problem with CRT screens, as do not have fixed pixels.  While ClearType was turned off by default in XP, it is now enabled by default in Windows 7 since the majority of computers purchased within the last 5 years came with LCD monitors.

  Tweak ClearType in Windows 7 for Better Screen Readability