svchost.exe
explorer.exe
spoolsv.exe
services.exe
lsass.exe
winlogon.exe
csrss.exe
smss.exe
System
System Idle Process

That's all you need.
I'm not even sure spoolsv is needed if you have no printer

Quick question then, because I'm always running WAY more processes than that...how can I kill a process that's being run by System? Since it tells me access is denied and all. I feel like such a dummy, but I've never really had to deal with this before; my computer's usually well protected.
Make sure you're logged in an administrator account. Either that, or it's spyware being really nasty, in which case, it should still be killable with Process Explorer - it's kind of like Task Manager on drugs