Just to make people aware, there is a new virus (technically ransomware (http://www.microsoft.com/security/resources/ransomware-whatis.aspx) ) that is doing the rounds. It’s been in the wild for a while, but seems to be getting more media attention these days.
Basically once you click on a e-mailed link it will encrypt files it can access on your hard drive. The engineering beauty of this virus is that it encrypts your files, and then contacts you to demand a ransom in the form of bit coins (http://bitcoin.org/en/) to decrypt your drive. So it becomes a case of pay up or your data is gone, if you have backups on another drive you should be able to restore to that drive, however if your do not have backups your data is basically gone as the encryption is uncrackable at the moment.
The above has a less chance of happening if you are running non system administrative privileges, You can read more about how a US police force had to pay to get there data back on the link below, it’s a pity they didn’t have backups. http://www.theguardian.com/technology/2013/nov/21/us-police-force-pay-bitcoin-ransom-in-cryptolocker-malware-scam
You can read more on: http://www.f-secure.com/weblog/archives/00002640.html