The Postcard from Hallmark hoax includes a link to a Snopes article which is worded in such a way that it appears the hoax warning is legitimate. It isn't. While greeting card scams do exist, they don't bear any resemblance to what's outlined in the hoax.

Chances are, there are dozens of security vulnerabilities waiting to be exploited on your system. And it's not just broken Windows you need to be concerned with. Adobe Flash, Acrobat Reader, Apple Quicktime, Sun Java and a bevy of other third-party apps may host security vulnerabilities waiting to be exploited. Secunia Software Inspector can make the discovery process a bit easier by providing a free online scanner to alert you to vulnerable software. >> Secunia Software Inspector