You are instructed to remove the error immediately. However, when you run a scan to remove the error, the scan does not run.
This error message indicates that the computer has been infected by the Win32/Alureon trojan virus.
The Alureon trojan virus is difficult to remove. This infection is identified by MSE as a rootkit in the master boot record. You can try steps to salvage your operating system. However, many IT professionals recommend that the operating system be reinstalled to make sure that the rootkit is removed.
Because you are using Microsoft Security Essentials, you can obtain assistance from MS Support with malware removal. To obtain assistance, follow these steps: