Helen, I just cleaned installed 7 with IE 8 and everything is very fast. I think that you have a bad installation. Try this, take your original installation DVD, insert it into your machine and go through the process as though you are going to install. However, at the point that you are asked, indicate that you want to make a repair. Basically anything that is not working correctly will be changed. I think that you will be happy with the outcome. Once you are happy, install all of your programs and make a system image. Save it. If you ever have a problem you can use the system image to make your OS, just like it was when you were satisfied. Let me know how it works out.
Check to be sure that your computer has the proper specs for 7.