The nasty must either add a totally new program, or infect (put a link to the nasty stuff, which it must also put somewhere. either at the end of the victim program, or as a separate lump) some regularly run bit.

"c:\program files\internet explorer\vvz.dll (Trojan.Agent) -> Quarantined and deleted successfully."

Looks like not part of a normal system (the name is often a clue) so was deleted. May also gave detected a 'signature' - a distinctive section of code.

There are 2 reasons why something may register as a problem in one of those sweeps

1) It may falsely register as a problem due to similarities in the code signature - called a False Positive - but very rare.

2) The nasty needs to hide a link inside some program that gets run regularly, often one that is running at the time of the infection - called being 'infected', so that each time the victim program is run, the nasty 'comes alive' again. Consequently it will have added to the file the stuff that gets recognised as the 'nasty bit'.

But it looks like you still have something nasty in the wood pile. Just because Malwarebyte found some stuff, doesn't mean it found it all.