Thank you for your replies, I think I would like to try Firefox, so do I have to uninstall IE7 before doing so? Any problems I might encounter as I am quite new to computers?
You will always have to have IE on your Windows machine, so you may as well keep it up to date.
When you first install Firefox it will ask you if you want it to be default browser. Just tick the 'yes' box.
When you next open IE it will ask the same thing - just tick 'no' and 'don't ask me this again'.
Be prepared to spend time to get to know Firefox. You can customise the way it looks, the tools you want by way of add ons and the bookmarks toolbar (favourites).