It's probably being recreated. There may be another process recreating the application, or, in a more extreme case, a driver. Take a look at all the start up processes(via msconfig, or other software).
Generally, a 'virus' which may be in the form of a driver, will have a counterpart, in the form of an executable. This is because many tasks can be perform in user-mode that cannot be performed in kernel-mode.
Chances are it's a keylogger or trojan of some sort, in thus case, I'd just reformat. Can never be too careful with that shiz.
There are two types of tragedies in life. One is not getting what you want, the other is getting it.
If you wake up at a different time in a different place, could you wake up as a different person?