If you disable everything in Startup then odds are some stuff wont work. What you want to do is stop any unnecessary programs and services. If you're not sure of what you're doing, don't change anything. If you feel like you can handle making these changes(which can screw things up if not careful) then read on.
For disabling Windows services, see this guide:
http://majorgeeks.com/page.php?id=12As it says near the top of the page, disable only a few things at a time, reboot and make sure everything works fine. That way if something gets screwed up it'll be easier to fix.
Anything not covered by that guide, Google the full process name, "whatever.exe". One of the first results should be from
http://www.liutilities.com. Keep in mind this will only tell you if a process is necessary or not. It will be up to you to decide if you want to disable it or not. If you're not sure, don't change it.