According to Mark Russinovich (author of the program) a better option with Process Explorer is to suspend processes- if a process is killed it may be started up again by another process which is monitoring it for just such an attempt to stop it. Once all malware processes have been identified and suspended, they can be killed.

http://www.microsoft.com/emea/itsshowtime/sessionh.aspx?videoid=359

(I watched this video somewhere without having to log on to MS, but can’t remember where now.)