A nickname for EMD SD9 locomotives, in reference to their smooth ride quality reminiscent of a Cadillac automobile. This nickname is said to have originated on the Southern Pacific Railroad.
Microsoft's Windows Malicious Software Removal Tool (MSRT) is a free program that removes a whole host of the most popular malicious software (malware). Many Windows users have it installed and run it monthly, yet are not aware of its existence.
No, that is probably not malware. It could be if it is in an unusual location, but mrtstub.exe is a component of the Microsoft Malicious Software Removal Tool. Right-click the executable, select properties, and check the Digital Signature tab. If it says it is signed by Microsoft Corporation, it is safe.