The message uses a little Windows Genuine Advantage fear mongering to cajole end users to download a fake update that realy is a backdoor Trojan. The message warns: "Please update your P.C. in maximum 12 hours otherwise your Windows will be Expired." Windows is going to expire alright, after it has been eaten by RATs, as in remote-access Trojans.
Microsoft doesn't solicit updates via e-mail. But how many people won't know this? Now that my teenage daughter is doing MySpace, I've reduced her Vista privileges. She gripes about my having to enter in administrator passwords, but malware-spiked MySpace pages and phishing e-mails like the aforementioned one have me concerned.