The following only applies to XP:
Right-click on your desktop, select properties, select the Appearance tab, click the Effects button and on the effects dialogue there's a drop-down that says "Use the following method to smooth the edges of screen fonts", select that drop-down and set it to "ClearType". Voila! Everything is now much prettier, including this site.
Now for all I know everyone who reads this has ClearType enabled and is thinking I'm a numpty for not knowing about it after three years of using XP but for those who don't this is a groovy discovery.