Oh gosh! Sorry - I didn't notice we'd gone onto a third page, and so kept refreshing the second one waiting for a reply.
The computer seems good for now, although I've mostly been studying for an exam happening later today and so haven't been on it that much. I do not know a lot about how backdoors and trojans work aside from the very general idea of "they get in and let other things in, but themselves hide," and so your early mention of increased vulnerability on this machine until a reformat gives me pause... how much stuff did ComboFix take off, and just how vulnerable is my computer? Should I disconnect it from the internet all times I'm not using the internet? Should I try to avoid internet usage on that machine? Can the backdoor allow a hacker to see stuff that happened on my machine pre-infection, or is it only important I have no sensitive documents and no sensitive transactions on the computer from there on out? Is there a way to get sensitive information deleted from my computer such that a hacker via backdoor cannot find it, or is anything that was on the machine post-infection liable? I have used this computer for banking in the past, but can stop now; but I need to use this machine, at least for word processing, for three more months, and really would benefit from internet usage on it as well. How should I proceed from here?
(I of course know that you cannot tell me exactly the correct course of action and do not hold you responsible for and damage I may cause by following your advice - I'm just looking for more information from sources more expert than myself)