aceplace57, see this post that I put up just a few minutes ago, in which I posted a whole bunch of “special characters”. How many of those does your system display?
I just fired up my XP laptop originally from about the same time period, and I’m not having any troubles. There were a couple symbols I didn’t have in Senegoid’s post, but I had most of them. And one of them I don’t even have on my Windows 7 computer.
Ultimately it’s down to what fonts you have, but I don’t have many that didn’t come with Windows XP on that laptop. Really, really old versions of Firefox would not do font substitution (which means that, if it can’t find a character in one font, it will pick the closest font that does have the character.)
I just remembered my even older computer that did have this problem. It seems that sometimes Windows XP doesn’t come with certain fonts enabled. I used Google and found some quick instructions that may help provide you with better Unicode support.