This site may help - http://pcsupport.about.com/od/findbyerrormessage/a/usp10-dll-not-found-missing-error.htm

I had this problem on my laptop. I tried the suggestions given on http://pcsupport.about.com/od/findbyerrormessage/a/usp10-dll-not-found-missing-error.htm to no avail. While messing with this I had searched my laptop for the usp10.dll -file and found that I had several copies, some newer than others. Going by old habits I copied the latest one to all folders where usp10.dll was. That did not work. Then Google took me to a Linux forum, actually Wine, that told me that different applications need different versions of the file. So the solution that worked for me was to copy the usp010.dll from my desktop computer; in folder Windows\System32 to the same folder on the laptop. In my case it is version 1.420.2600.5512, 406 016 bytes, dated April 14, 2008. And here I am, running Firefox fine and dandy. Try it! I think my problem was originally caused by an aborted online update of Windows XP.