This article on a new virus that's been making the rounds is a fascinating combo of natural curiosity, social engineering and cleverly malicious code. Basically, code is written into a PNG file and the user is instructed to resave the image from MSPaint as an HTA - which uncompresses the code and allows it to run as an HTML Application. The most interesting part, to me, is that the damage is self inflicted - your own curiosity is your downfall.