A new trojan that began spreading last week is wreaking havoc on Windows machines everywhere, with an estimated 1.6 million infections in just four days according to Symantecs detection reports. Called “Storm” and also "Peacomm", it is unique in that it may also be able to infect Windows Vista, if an infected email made it to the system:

Microsoft's soon-to-release-to-consumers Vista, however, does appear at risk, added Symantec Tuesday. "It appears most if not all variants could execute on Vista," the spokesman said. "The only way the Trojan would be unsuccessful is if somehow Vista is able to detect/prohibit the e-mail. This seems unlikely."
A few fixes and suggestions have been posted, though up to date anti-virus scanners should be able to detect and remove it. Interestingly enough, the code of the worm is designed to specifically ignore Windows Server 2003, but will still target 2000 and XP machines.