Problem w/OE6

I have Windows XP, Version 5.1, w/Outlook Express 6. I am unable to change the fonts, have searched the net and tried many different things and now am unable to do anything. When I copy my text when I compose, then go to the pulldown meu to change the size, I can't change it. I was going to "format," then "encoding," then changing it to "Baltic (ISO)," and for some reason that worked, but now it doesn't. I've tried all the options I've found on the computer on various websites, and now am more stuck than ever. I use Firefox for my default browser but do go to Explorer now and then, and I did hit the "View text size" as larger on some site, but that's the only thing I can think of that I've done differently, and don't see how that could matter. And ideas are greatly appreciated.