Many people are being hit by fake emails from Microsoft these days. You should not follow what the email tells you to do, which is to download an update from Microsoft. The email makes it look like you are downloading from Microsoft but you are not. Instead you are downloading a keylogger from somewhere else. For those of you who don’t know keyloggers I can assure you that it’s not something you want on your PC. A keylogger simply logs everything you write and then send it to the guy who made it. That means that you’ll be giving him your credit card number, password, ect. if you download the keylogger.
If you ever want to update your windows system you should always go to Microsoft’s own site. Personally I never trust emails sent to me with requests about updating this and that. One thing you should always do is to simply read their homepage. You can pretty much count on the fact that if it’s important enough to email then it’s also important enough to put on their homepage. See some of my useful links below.

Read more about the fake email at Sophos.com
Microsoft.com Update
My page with lots of security advice