the safest way is to learn to make a coffee just after pressing the on button
failing that
some of the startup options and utilities can be seen by typing msconfig into the start option and looking through the list
but I like to use
http://mlin.net/StartupCPL.shtml
it's small - but uses a wastebin so you can generally undo even the worst cockups
things like pdf spoolers and tomtom home are no brainers .... but what about ctfmon (which is used by MS Office)
there isn't a formula for what will and what wont
you'll have to list them all
identify them using google
disable them ... and see
(and seeing could take a few weeks ... I connect my tom tom about every 3 months .... it just might be that plugging it in will cause a crash if I'm printing a PDF)
then there are the 100000000s of services windows runs
right click my computer | manage | computer management | services and applications | services
and then there is ..... and then
google speedup windows or similar .... you'll get 1000000s of hits
be afraid .... very afraid - because some sites
http://www.askdavetaylor.com/speed_up_windows_ xp_startup.html
are quite conservative
some are verry aggressive .... some are just bl@@dy rubbish
the simplest "no brainer" can cause utter chaos .... and disabling core services will not affect a thing ... if you don't use whatever it is
but stay away from the winoptimizer
type progs ... because they are all definitely a waste of money