The Internet Archive has recently released The Malware Museum, a collection of old viruses and malware from the eighties and nineties.
The idea behind the "museum" is to experience what it was like to have your computer infected with a virus, back in the day when there was no internet and hardly any anti-virus software available.
The malware on this site is usually so old you need to use an emulator (such as DOSBox) and has been stripped from all malicious code, leaving only the on-screen messages intact.
A comprehensive guide on removing the I Want This adware can be found on the forums of Spybot S&D.
Direct link: http://forums.spybot.info/showthread.php?t=65998.