should I re-install windows and/or internet explorer?

My computer won't let me open email attachments, download updates or anything else, it won't print, and when I try to open internet options nothing happens. I have Windows XP Media Center 2005 and recently updated to IE 7, which I suspect may be the problem, but I don't know for sure. I sure could use some help from someone way smarter than I am about these things. You'd have my sincerest gratitude if you can help me out. Thanks!

Paula

 

Thanks PrivatePile-sir. We found a trojan, got rid of it and reinstalled IE7,too. Everything works great now thanks to you! I really appreciate your advice.
Sincerest Thanks!