If you have Windows Vista or Windows 7, during the install process, you'll see "Upgrade". Chose that option.
The upgrade option is safe for all your files, settings and installed programms and application.
Run an antivirus as soon as possible.
Make sure that your computer is ALWAYS up to date by having the auto-update active. It must at least download the updates and ask you, or be set to automaticaly download and install updates.
Another thing would be to use some other browser than Internet Explorer, like (by alphabetical order, not preference) Chrome, Firefox or Opera. ALL are available for free and are good.
NEVER EVER install anything asked by any adult sites to view the content!!! Be wary if ANY site ask you to install anything to view the content and ABSOLUTELY NEVER EVER get any content from any pop-up or proposed link.
Several are fronts for criminals or have been compromised in one way or another. If it appens again, just go elsewhere. You may also take some time to block that site so that you won't stumble upon it later.
Electro, October 2012