A rootkit is a malicious software that uses stealth techniques to hide its presence from not only the user but also from the operating system (Windows) itself. A rootkit often takes the elevated administrator privileges on your system and then infect the system as it pleases. A rookit is the hardest type of malware to remove from your system. There are some rootkits like Vundo which can be fully removed only after formatting your hard disk. Malwarebytes, the makers of the popular Malwarebytes Anti-malware software, have come up with Malwarebytes Anti-rootkit which can help your detect and remove possible rootkits infections on your system.
You can download Malwarebytes Anti-Rootkit from the Malwarebytes website. The download is a portable application inside a ZIP archive. Just extract the content of the ZIP archive to a folder and double-click on mbar.exe from there, in order to run Malwarebytes Anti-Rootkit. When it starts it installs a DDA driver to check the presence of a rootkit on your system. After this it would show the main window where you can update its program database.
After the update is completed, you can click on the Next button to move on to the scan section. Here you can choose which areas of your system you want to scan for rootkits. You can choose from drivers, sectors and system. Clicking on the Scan button would initiate the scanning process.
The scan can take many minutes to complete. After this it would show you the results of how many rootkits it finds on your system. You should select all the rootkits in the found for removal. There is an option for creating a restore point which is automatically selected. You can click on the Cleanup button to clean up the found malware.
Now you have to wait while the system shuts down and the cleanup process is performed. After Windows restarts, you can scan your system again to see if Malwarebytes Anti-Rootkit finds any more malware files on your computer. It also includes a tool called fixdamage.exe which can repair basic system services like Windows Update, Windows Firewall etc. After running fixdamage.exe, you should restart your system, even if this tool does not prompt you to.
You can download Malwarebytes Anti-Rootkit from http://www.malwarebytes.org/products/mbar/.