Mara - the best thing to do is open msconfig and then expand the command part of the window, from there it is pretty self explanatory - if you do not understand then as you say leave alone.
if you do then most people disable what they 'feel' they do not need, for example if you use Adobe to view files and there are 3 startup options containing Adobe - then chances are you do not need them, unless you edit and create PDF's.