What is MalwareBell?
It is a rogue computer security software, which tends to exaggerate PC scan reports in order to scare user, and that is why MalwareBell (Malware Bell) is also known as a scareware. The program displays "System Error" messages that warn user of malware infections and ask to download antivirus software to eliminate threats. Computer scan process will be launched right after MalwareBell has been installed, which will generate a report in the end containing non-existent threats or non-spyware applications, which are being considered as malicious objects.
"System Error!" alert:

Under the influence of a trojan, Google search engine results will now be corrupted, containing adult related links and an advertisement of MalwareBell, which alerts user about his browser being hijacked convincing user to download the program.
Google corrupt search results affected by Malware Bell:

Author: malwarebell.com
"System Error!" alert:

Under the influence of a trojan, Google search engine results will now be corrupted, containing adult related links and an advertisement of MalwareBell, which alerts user about his browser being hijacked convincing user to download the program.
Google corrupt search results affected by Malware Bell:

Author: malwarebell.com
MalwareBell removal tool:
- Spyware Doctor (see here for the installation guide)
Screenshot:

MalwareBell Entries:
The following files are created: mb.exe (setup file), malwarebell.exe