This week, alongside the January security updates, Microsoft released the first version of its malware removal tool, called the Microsoft Windows Malicious Software Removal Tool (MSRT). New versions will be released on the second Tuesday of each month (with the monthly security updates) and each version will be cumulative.
Note that this is not the Microsoft Windows AntiSpyware tool (a separate beta of that product was released last week, based on the anti-spyware application gained in the purchase of Giant Company), nor is it an anti-virus tool - MSRT is simply a rollup of all the malware removal utilities that Microsoft has previously released.