Watch out for those web sites that have animated cursors. Especially make sure you don't surf to those with Internet Explorer unless you want to leave your computer vulnerable to hackers.
Microsoft has issued a notice that it is investigating the vulnerability. If users visit a web site or view an e-mail containing hacked .ani files (the animated cursor file type), so Microsoft's advice for the moment: be careful when opening unsolicited emails or browsing new web sites.
The vulnerability appears to affect Internet Explorer 6 and 7 running on Windows XP SP2.
All the more reason to switch to either Firefox or Opera for you browser.
Microsoft Security Advisory (935423)
Title: Vulnerability in Windows Animated Cursor Handling