You need to get Mike Lin's companion program Startup Monitor
(
http://www.mlin.net). It runs completely transparently in the background
and catches every attempt by every program to register itself to start up
with Windows. Here's the program description from the web site:
StartupMonitor is a small utility that runs transparently (it doesn't even
use a tray icon) and notifies you when any program registers itself to run
at system startup. It prevents those utterly useless tray applications from
registering themselves behind your back, and it acts as a security tool
against trojans like BackOrifice or Netbus.
StartupMonitor does not require Startup Control Panel, but it complements it
nicely. When you choose not to allow a program to register itself, the
program's entry becomes disabled in Startup Control Panel, so you can go
back and enable it later if necessary. StartupMonitor watches the Start
Menu's Startup folders and the Run entries in the registry.
I have been using both for quite a while and they do an excellent job. No
program has been able to slip in behind my back. You might want to give it a
look.