I can't see hidden folders or open tskmgr

so the problem i have is on my fathers computer. now it wouldnt be much of a problem except for the fact that i somtimes use it. so i have a usb stick and some of the files on it are hidden but i cant see the files because of a recent virus that was on my fathers computer, trojan virus. actually it was 16 viruses(or 1 broken up in to 16 part, whatever) and because of this the computers function was limited. symptoms: the operating system wouldnt start up on its owm. i would but the explorer program to run it all wouldnt start, and its windows vista, so it makes even more annoying whenever something needed permission to run because that permission thing would disengage the explorer. well all that was fixed but some things are still missing: the thing in the tools menu of the windows explorer that lets you choose to show hidden folders, and the task manager is missing from the options when we hit [ctrl]+[alt]+[delete]. i tried the run thing to fix it but it didnt work for vista as it did XP(i had that problem for that too). so if you know a solution to any or all of these problems, that dont cost, btw, i would be truely thankfull.