Hi Timothee,
Yes you have fallen victim to a rogue program or scumware, SpyTrooper, part of the smitfraud group of malware vendors.
Look for instructions here:
http://answers.google.com/answers/threadview?id=703813Install siteadvisor as an add-on for IE or FF, or download the DrWeb hyperlink pre-scanner add-on for your browser to stay away from rogue programs and spammers.
After your comp is cleansed, install one good resident anti-virus program (Avast), scan occasionally with a good online scanner like Bitdefender, have one good software firewall like ZA for instance, install the three anti-spyware programs recommended: Spybot S&D, SpywareBlaster and Ad-Aware (all free), scan occasionally with spyaudit online scanner for ad-spyware and tracking cookies. Surf safe, stay malware free, is the wish of,
polonus