On Tuesday, Microsoft released a massive 13 security updates to patch 34 vulnerable holes in Windows. Adobe released one update to patch 29 vulnerabilities in Reader and Acrobat. All of these updates are considered critical.
Go directly to Microsoft's website to find out more about their updates and if they are applicable to your system: http://www.microsoft.com/security/updates/bulletins/200910.aspx
Go directly to Adobe's website to find out more about their updates: http://www.adobe.com/support/security/bulletins/apsb09-15.html
For more information about system patching, check out "System Patching: When is the right time?"