FYI - SVHost.exe describes exactly what it is - "A Service Host"
Writing a true windows service is not trivial as the interaction with SCM can be quite complex - I have written a few and it takes a long time to sort out the interaction with the operating system before you even get around to sorting out what the service is meant to be doing.
Microsoft in their ultimate wisdom wrote what us programmers term as a wrapper named svchost.exe - this does all the interaction with the operating system and then calls your library based code (a Dynamic Linked Library - DLL)
Whilst this has effectively made service writing a possibility for even the numpties of the world it has left people on some operating systems with little exposure to what is actually running - hence on vista you can see the actual command line required to start.
A similar issue exists with RunDLL.exe although this does not run as a service it is very cryptic to find out what is running and why.
Killing off services and programs when running is not a sensible thing to do unless you truly know what your doing - if you do then go to service control manager (SCM) and prevent it running in the first place. If you dont then be cautious -most services sit idle waiting for the moment you need them - you can kill them off and not know you need them until you actually do and then experience problems.
Whilst it is true that some services may never be required killing them off will give you little as a properly written service will remain idle until required and will take very little memory.