Microsoft had a ton of patches that were released and were critical in nature:

The first, was a critical rollup for Internet Explorer 8 and older (pretty much if you use IE, you were affected). Some of the exploits allowed a remote attacker to gain control of your computer, it’s actually a pretty interesting  exploit that involves just having you, as a user, just view the page.  Note that you don’t have to interact with it, just click the link and you are toast.   Updates are for free at http://windowsupdate.microsoft.com

The second, was a patch for Outlook XP, 2003, 2007 and Visio Viewer for 2003 and 2007.  Three particular issues can grant a hacker or automated program access to your machine, with your access without these patches… Checkout http://officeupdate.microsoft.com for the free patches, note the top right of the page that says “Check for Updates” as the page is a little disorganized.

The third group, is 11 patches, with six of them being critical that range in all sorts of issues for a lot of programs that everyone has installed on their machines.  Checkout http://windowsupdate.microsoft.com if you haven’t and just get the free updates.