I've used these tools for finding servu. They're free, simple but powerful enough to detect any serv-u on your system.
tlist.exe - tasklist viewer, i prefer it over many other similar tools 'cause it's ability to display full path and switches/attributes used to run program - good for recognising which svchost is fake

... and not only for this

)
kill.exe - kills tasks
sc.exe - standard M$ utility to control services - comes with XP - can do almost anything with services - works on NT, w2k too
This and some experience is the most dangerous weapon against serv-u

Ahh... almost forgot to tell. To get these tools - google for them

EDIT:
There's even an easier way to find serv-u but i don't know which prog can help you.
Serv-U when running always creates a handle called RWinSocket. If only someone could tell me the name of program similar to tlist.exe but which can gives information about created handles too.... Anyone knows a small free cli utility like that.
(Sorry for bad english)