Microsoft Security Essentials (aka Morro) Available for Limited Download
Windows only: We've been keeping you up to date on Morro, Microsoft's free anti-malware now officially known as Microsoft Security Essentials, since it first hit the rumor-mill. If you're eager to try it out, MSE beta is available for download now.
The catch: Microsoft is capping MSE downloads at 75,000, so get it while it's hot. According to ZDNet, the download was supposed to be available at 9PST, but it's 8:20 now and I was able to download it without a problem.
Also according to ZDNet, you'll need to be in the U.S., Israel, or Brazil to try out the beta, and like most early downloads from Microsoft, you'll need to sign in with a Live account to get rolling (I also had to complete a Microsoft Connect registration and a survey). MSE is available for Windows XP, Vista, and Windows 7 (including both 32- and 64-bit for Vista and Windows 7).
Update: Your computer will also need to pass the whole Windows Genuine Advantage validation, so hopefully you're legit.
copy-paste from Lifehacker