If you get an email claiming that you've won a Macbook Air, don't believe it.
It's another email virus; this time, a variant of the Zbot trojan.
There are other reports on the Internet about a virus-laden message with the exact same text, but it's not the same virus. That one is detected by over 70% of virus scanners. This one is detected by only 30%.
The subject line of the email is short, merely:
Congratulations
The body text of the email is:
Congratulations!! You have won todays Macbook Air.
Please open attached file and see datails.
Notice the spelling mistake in "datails."
The attachment shows as a 103 Kilobyte zip file.
This trojan appears to be an encrypted version of the original ZBot, which was designed to steal passwords for banking and other financial sites.