Windows Autoruns
Looking to clean some junk out of your Windows startup?
The guys at SysInternals, who produce some of the best free Windows utilities, have a utility calls Autoruns, that can really help.
Autoruns knows all the places that things can hook into Windows. Browser helper objects (BHO's), shell extensions, print monitors, and lots more.
Cleaning up what gets launched when your system boots can significantly reduce startup time, and free up memory. But...
Generally, turning off anything that's supplied by Microsoft is a bad idea. Sure there are some things you can disable, but unless you really know what it is you're disabling, this tool makes it easy to turn off some core services (like the Explorer itself).