change default font

Hi,

I'm using windows XP and i have installed the right to left language
support. Now i have added the keyboard for my local language too. This
enables me to type in my local language. Even rename files in my language,
etc. too. But windows has only one font (also the defualt font) for that
language which i don't find very nice. So i got some other new fonts
designed for use in XP for that language. I want to change the default font
for that language to one of those new fonts.
So can anybody tell me how??

Thanks.