I had one this morning.... It looks like its from Microsoft, it has copyright Microsoft all over it. It arrived in my email with an attachment.
It is NOT from Microsoft. Microsoft do not send patches by email and are highly unlikely to ever do so. Please do NOT open or run the attachment.
If you want patches for Microsoft products (and we highly recommend you DO patch regularly to keep yourselves up to date) its extremely quick, and extremely easy to do. Please visit windowsupdate.microsoft.com it is free, it is very easy and it will help prevent your PC catching any nasty illneses from these worms that arrive in your Inbox! Not to mention it keeps everything else up to date like Media Player, DirectX etc etc.
Go update, and DONT open any attachments that claim to have come from Microsoft. They didn't send it.