Microsoft has issues 12 fixes today (yup - it's Patch Tuesday), including seven, which have been classified as critical.
The critical vulnerabilities affect Internet Explorer and Media Player on all contemporary operating systems so Windows 2000, XP and Vista, Windows Server 2003 and 2008.
These patches deal specifically with remote code execution which allows hackers to control a computer without the computer owner realising it.
The five non-critical patches target Microsoft's Office applications: Access, Excel and Powerpoint.
There are also fixes in there for Outlook Express, MSN Messenger and Word as well as an upgrade to the Windows Malicious Software Removal Tool.
The updates are available through the Microsoft Update website or through your automatic update tool.