This indicates an attack attempt against a buffer overflow vulnerability in the "IsComponentInstalled" method in Internet Explorer.
The vulnerability is caused by insufficient checks of parameters when the vulnerable software handles a call to "IsComponentInstalled" with a long first parameter. It allows a remote attacker to execute arbitrary code.
Internet Explorer 6.0 on Windows 2000 pre-SP4 or Windows XP pre-SP1
System Compromise: Remote attackers can gain control of vulnerable systems.
Upgrade to Windows 2000 SP4 or Windows XP SP1.