I was trying to register on a forum where you type in a code you see in a box and the site just wouldn´t accept the code I typed in (Some of those codes are hard to read but this was easy.) After many unsuccessful tries I contacted the site and they said I should try changing browsers. My computer came with Windows Vista. How do you "change browsers"?

Try Firefox, just do a search on it and its freeware. You can have as many browsers as you want on your system. Just launcgh Firefox instead of IE.