Download IE8 from here
Get on a computer where you can download IE8 (you could probably use Firefox on your computer) from here
http://www.microsoft.com/en-us/download/details.aspx?id=43 and install IE8. I haven't had any problems with it, maybe that's because I have the latest maintenance for it. Once you get it installed, you should download and install all the recommended Windows updates (but not the optional ones).
I guess you know that MS is going to pull the plug on XP at the end of this year, so if you plan to stay with it, you'd better get it up to speed while you can. Since new software isn't likely to support XP starting next year, I'd make plans to upgrade to Windows 7 if you can.